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	$161.31	3.632%	$167.1688	$167.17	$167.15	$167.20
Purchase #2	$234.46	3.282%	$242.155	$242.16	$242.15	$242.20
Purchase #3	$154.76	8.746%	$168.2953	$168.30	$168.30	$168.30
Purchase #4	$114.31	11.717%	$127.7037	$127.70	$127.70	$127.70
Purchase #5	$91.39	6.838%	$97.6392	$97.64	$97.65	$97.60
Purchase #6	$44.54	13.614%	$50.6037	$50.60	$50.60	$50.60
Purchase #7	$155.86	6.366%	$165.782	$165.78	$165.80	$165.80
7 purchase totals =	$956.63		$1,019.3477	$1,019.35	$1,019.35	$1,019.40