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	$191.27	9.346%	$209.1461	$209.15	$209.15	$209.10
Purchase #2	$50.58	11.131%	$56.2101	$56.21	$56.20	$56.20
Purchase #3	$83.38	6.817%	$89.064	$89.06	$89.05	$89.10
Purchase #4	$74.57	10.572%	$82.4535	$82.45	$82.45	$82.50
Purchase #5	$65.77	7.433%	$70.6587	$70.66	$70.65	$70.70
Purchase #6	$95.76	8.792%	$104.1792	$104.18	$104.20	$104.20
Purchase #7	$244.76	7.480%	$263.068	$263.07	$263.05	$263.10
7 purchase totals =	$806.09		$874.7796	$874.78	$874.75	$874.90