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	$63.33	13.204%	$71.6921	$71.69	$71.70	$71.70
Purchase #2	$191.56	4.153%	$199.5155	$199.52	$199.50	$199.50
Purchase #3	$229.77	12.193%	$257.7859	$257.79	$257.80	$257.80
Purchase #4	$195.57	11.718%	$218.4869	$218.49	$218.50	$218.50
Purchase #5	$197.71	6.199%	$209.966	$209.97	$209.95	$210.00
Purchase #6	$59.80	11.183%	$66.4874	$66.49	$66.50	$66.50
Purchase #7	$72.39	11.766%	$80.9074	$80.91	$80.90	$80.90
7 purchase totals =	$1,010.13		$1,104.8412	$1,104.86	$1,104.85	$1,104.90