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	$99.60	11.700%	$111.2532	$111.25	$111.25	$111.30
Purchase #2	$65.96	10.518%	$72.8977	$72.90	$72.90	$72.90
Purchase #3	$74.93	9.673%	$82.178	$82.18	$82.20	$82.20
Purchase #4	$64.33	12.124%	$72.1294	$72.13	$72.15	$72.10
Purchase #5	$17.80	10.765%	$19.7162	$19.72	$19.70	$19.70
Purchase #6	$67.51	9.572%	$73.9721	$73.97	$73.95	$74.00
Purchase #7	$211.29	11.444%	$235.47	$235.47	$235.45	$235.50
7 purchase totals =	$601.42		$667.6166	$667.62	$667.60	$667.70