Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$171.90	7.123%	$184.1444	$184.14	$184.15	$184.10
Purchase #2	$172.59	10.223%	$190.2339	$190.23	$190.25	$190.20
Purchase #3	$189.59	6.159%	$201.2668	$201.27	$201.25	$201.30
Purchase #4	$188.36	13.839%	$214.4271	$214.43	$214.45	$214.40
Purchase #5	$245.48	11.337%	$273.3101	$273.31	$273.30	$273.30
Purchase #6	$158.61	3.522%	$164.1962	$164.20	$164.20	$164.20
Purchase #7	$233.36	13.502%	$264.8683	$264.87	$264.85	$264.90
7 purchase totals =	$1,359.89		$1,492.4468	$1,492.45	$1,492.45	$1,492.40