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	$140.34	7.704%	$151.1518	$151.15	$151.15	$151.20
Purchase #2	$98.80	6.692%	$105.4117	$105.41	$105.40	$105.40
Purchase #3	$224.93	7.741%	$242.3418	$242.34	$242.35	$242.30
Purchase #4	$42.62	3.668%	$44.1833	$44.18	$44.20	$44.20
Purchase #5	$119.36	5.367%	$125.7661	$125.77	$125.75	$125.80
Purchase #6	$111.52	6.362%	$118.6149	$118.61	$118.60	$118.60
Purchase #7	$102.51	8.408%	$111.129	$111.13	$111.15	$111.10
7 purchase totals =	$840.08		$898.5986	$898.59	$898.60	$898.60