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	$118.75	10.451%	$131.1606	$131.16	$131.15	$131.20
Purchase #2	$148.36	9.358%	$162.2435	$162.24	$162.25	$162.20
Purchase #3	$156.70	11.525%	$174.7597	$174.76	$174.75	$174.80
Purchase #4	$232.30	10.398%	$256.4546	$256.45	$256.45	$256.50
Purchase #5	$137.34	3.773%	$142.5218	$142.52	$142.50	$142.50
Purchase #6	$38.66	8.515%	$41.9519	$41.95	$41.95	$42.00
Purchase #7	$116.29	7.335%	$124.8199	$124.82	$124.80	$124.80
7 purchase totals =	$948.40		$1,033.9120	$1,033.90	$1,033.85	$1,034.00