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	$113.47	11.326%	$126.3216	$126.32	$126.30	$126.30
Purchase #2	$191.85	7.730%	$206.68	$206.68	$206.70	$206.70
Purchase #3	$90.89	9.497%	$99.5218	$99.52	$99.50	$99.50
Purchase #4	$214.65	6.477%	$228.5529	$228.55	$228.55	$228.60
Purchase #5	$131.91	12.658%	$148.6072	$148.61	$148.60	$148.60
Purchase #6	$56.34	11.697%	$62.9301	$62.93	$62.95	$62.90
Purchase #7	$142.81	10.281%	$157.4923	$157.49	$157.50	$157.50
7 purchase totals =	$941.92		$1,030.1059	$1,030.10	$1,030.10	$1,030.10