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	$155.27	3.136%	$160.1393	$160.14	$160.15	$160.10
Purchase #2	$71.59	12.684%	$80.6705	$80.67	$80.65	$80.70
Purchase #3	$180.58	5.596%	$190.6853	$190.69	$190.70	$190.70
Purchase #4	$150.27	5.598%	$158.6821	$158.68	$158.70	$158.70
Purchase #5	$93.94	6.769%	$100.2988	$100.30	$100.30	$100.30
Purchase #6	$97.46	8.508%	$105.7519	$105.75	$105.75	$105.80
Purchase #7	$232.68	5.682%	$245.9009	$245.90	$245.90	$245.90
7 purchase totals =	$981.79		$1,042.1288	$1,042.13	$1,042.15	$1,042.20