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	$165.99	4.282%	$173.0977	$173.10	$173.10	$173.10
Purchase #2	$105.73	3.456%	$109.384	$109.38	$109.40	$109.40
Purchase #3	$175.66	12.403%	$197.4471	$197.45	$197.45	$197.40
Purchase #4	$245.46	3.439%	$253.9014	$253.90	$253.90	$253.90
Purchase #5	$80.37	11.507%	$89.6182	$89.62	$89.60	$89.60
Purchase #6	$204.61	8.311%	$221.6151	$221.62	$221.60	$221.60
Purchase #7	$9.83	10.306%	$10.8431	$10.84	$10.85	$10.80
7 purchase totals =	$987.65		$1,055.9066	$1,055.91	$1,055.90	$1,055.80