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	$153.83	7.712%	$165.6934	$165.69	$165.70	$165.70
Purchase #2	$115.95	12.694%	$130.6687	$130.67	$130.65	$130.70
Purchase #3	$84.34	6.265%	$89.6239	$89.62	$89.60	$89.60
Purchase #4	$87.30	4.760%	$91.4555	$91.46	$91.45	$91.50
Purchase #5	$52.50	4.568%	$54.8982	$54.90	$54.90	$54.90
Purchase #6	$51.28	5.196%	$53.9445	$53.94	$53.95	$53.90
Purchase #7	$198.85	5.277%	$209.3433	$209.34	$209.35	$209.30
7 purchase totals =	$744.05		$795.6275	$795.62	$795.60	$795.60