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	$151.47	9.384%	$165.6839	$165.68	$165.70	$165.70
Purchase #2	$248.77	11.283%	$276.8387	$276.84	$276.85	$276.80
Purchase #3	$207.81	6.485%	$221.2865	$221.29	$221.30	$221.30
Purchase #4	$190.59	4.284%	$198.7549	$198.75	$198.75	$198.80
Purchase #5	$140.52	4.801%	$147.2664	$147.27	$147.25	$147.30
Purchase #6	$82.73	8.787%	$89.9995	$90.00	$90.00	$90.00
Purchase #7	$33.70	9.476%	$36.8934	$36.89	$36.90	$36.90
7 purchase totals =	$1,055.59		$1,136.7233	$1,136.72	$1,136.75	$1,136.80