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	$136.82	8.302%	$148.1788	$148.18	$148.20	$148.20
Purchase #2	$176.36	11.506%	$196.652	$196.65	$196.65	$196.70
Purchase #3	$150.39	8.210%	$162.737	$162.74	$162.75	$162.70
Purchase #4	$80.55	12.610%	$90.7074	$90.71	$90.70	$90.70
Purchase #5	$83.49	6.719%	$89.0997	$89.10	$89.10	$89.10
Purchase #6	$50.64	10.450%	$55.9319	$55.93	$55.95	$55.90
Purchase #7	$136.90	11.336%	$152.419	$152.42	$152.40	$152.40
7 purchase totals =	$815.15		$895.7258	$895.73	$895.75	$895.70