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	$138.32	8.129%	$149.564	$149.56	$149.55	$149.60
Purchase #2	$37.46	12.253%	$42.05	$42.05	$42.05	$42.10
Purchase #3	$156.61	5.217%	$164.7803	$164.78	$164.80	$164.80
Purchase #4	$244.90	8.321%	$265.2781	$265.28	$265.30	$265.30
Purchase #5	$162.43	7.846%	$175.1743	$175.17	$175.15	$175.20
Purchase #6	$107.84	11.459%	$120.1974	$120.20	$120.20	$120.20
Purchase #7	$170.85	13.778%	$194.3897	$194.39	$194.40	$194.40
7 purchase totals =	$1,018.41		$1,111.4338	$1,111.43	$1,111.45	$1,111.60