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	$77.73	10.412%	$85.8232	$85.82	$85.80	$85.80
Purchase #2	$232.40	7.777%	$250.4737	$250.47	$250.45	$250.50
Purchase #3	$59.73	4.814%	$62.6054	$62.61	$62.60	$62.60
Purchase #4	$53.49	4.490%	$55.8917	$55.89	$55.90	$55.90
Purchase #5	$13.70	6.712%	$14.6195	$14.62	$14.60	$14.60
Purchase #6	$79.85	7.268%	$85.6535	$85.65	$85.65	$85.70
Purchase #7	$204.27	3.543%	$211.5073	$211.51	$211.50	$211.50
7 purchase totals =	$721.17		$766.5743	$766.57	$766.50	$766.60