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	$82.98	3.110%	$85.5607	$85.56	$85.55	$85.60
Purchase #2	$205.59	6.616%	$219.1918	$219.19	$219.20	$219.20
Purchase #3	$169.81	11.184%	$188.8016	$188.80	$188.80	$188.80
Purchase #4	$150.29	9.445%	$164.4849	$164.48	$164.50	$164.50
Purchase #5	$141.60	11.854%	$158.3853	$158.39	$158.40	$158.40
Purchase #6	$248.65	13.135%	$281.3102	$281.31	$281.30	$281.30
Purchase #7	$88.83	3.115%	$91.5971	$91.60	$91.60	$91.60
7 purchase totals =	$1,087.75		$1,189.3316	$1,189.33	$1,189.35	$1,189.40