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	$97.53	9.205%	$106.5076	$106.51	$106.50	$106.50
Purchase #2	$67.63	7.148%	$72.4642	$72.46	$72.45	$72.50
Purchase #3	$214.97	7.815%	$231.7699	$231.77	$231.75	$231.80
Purchase #4	$89.64	11.370%	$99.8321	$99.83	$99.85	$99.80
Purchase #5	$118.58	9.774%	$130.17	$130.17	$130.15	$130.20
Purchase #6	$19.75	3.754%	$20.4914	$20.49	$20.50	$20.50
Purchase #7	$158.51	7.747%	$170.7898	$170.79	$170.80	$170.80
7 purchase totals =	$766.61		$832.0250	$832.02	$832.00	$832.10