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	$211.47	9.287%	$231.1092	$231.11	$231.10	$231.10
Purchase #2	$55.33	8.170%	$59.8505	$59.85	$59.85	$59.90
Purchase #3	$107.99	7.823%	$116.4381	$116.44	$116.45	$116.40
Purchase #4	$142.35	7.352%	$152.8156	$152.82	$152.80	$152.80
Purchase #5	$29.75	10.178%	$32.778	$32.78	$32.80	$32.80
Purchase #6	$84.89	11.542%	$94.688	$94.69	$94.70	$94.70
Purchase #7	$117.38	9.591%	$128.6379	$128.64	$128.65	$128.60
7 purchase totals =	$749.16		$816.3173	$816.33	$816.35	$816.30