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	$165.94	5.222%	$174.6054	$174.61	$174.60	$174.60
Purchase #2	$221.68	3.416%	$229.2526	$229.25	$229.25	$229.30
Purchase #3	$26.91	12.333%	$30.2288	$30.23	$30.25	$30.20
Purchase #4	$32.55	12.804%	$36.7177	$36.72	$36.70	$36.70
Purchase #5	$181.38	8.415%	$196.6431	$196.64	$196.65	$196.60
Purchase #6	$167.86	13.271%	$190.1367	$190.14	$190.15	$190.10
Purchase #7	$33.96	12.292%	$38.1344	$38.13	$38.15	$38.10
7 purchase totals =	$830.28		$895.7187	$895.72	$895.75	$895.60