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	$109.73	10.188%	$120.9093	$120.91	$120.90	$120.90
Purchase #2	$115.84	3.207%	$119.555	$119.56	$119.55	$119.60
Purchase #3	$198.61	10.426%	$219.3171	$219.32	$219.30	$219.30
Purchase #4	$239.65	6.545%	$255.3351	$255.34	$255.35	$255.30
Purchase #5	$77.71	7.388%	$83.4512	$83.45	$83.45	$83.50
Purchase #6	$104.36	13.698%	$118.6552	$118.66	$118.65	$118.70
Purchase #7	$96.45	9.142%	$105.2675	$105.27	$105.25	$105.30
7 purchase totals =	$942.35		$1,022.4904	$1,022.51	$1,022.45	$1,022.60