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	$116.86	4.162%	$121.7237	$121.72	$121.70	$121.70
Purchase #2	$179.61	4.804%	$188.2385	$188.24	$188.25	$188.20
Purchase #3	$187.97	4.205%	$195.8741	$195.87	$195.85	$195.90
Purchase #4	$143.37	11.651%	$160.074	$160.07	$160.05	$160.10
Purchase #5	$237.57	7.312%	$254.9411	$254.94	$254.95	$254.90
Purchase #6	$106.87	4.711%	$111.9046	$111.90	$111.90	$111.90
Purchase #7	$69.76	4.189%	$72.6822	$72.68	$72.70	$72.70
7 purchase totals =	$1,042.01		$1,105.4382	$1,105.42	$1,105.40	$1,105.40