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	$95.59	10.796%	$105.9099	$105.91	$105.90	$105.90
Purchase #2	$202.26	13.149%	$228.8552	$228.86	$228.85	$228.90
Purchase #3	$236.82	13.568%	$268.9517	$268.95	$268.95	$269.00
Purchase #4	$57.42	6.804%	$61.3269	$61.33	$61.35	$61.30
Purchase #5	$32.29	5.403%	$34.0346	$34.03	$34.05	$34.00
Purchase #6	$212.51	4.857%	$222.8316	$222.83	$222.85	$222.80
Purchase #7	$203.80	3.722%	$211.3854	$211.39	$211.40	$211.40
7 purchase totals =	$1,040.69		$1,133.2953	$1,133.30	$1,133.35	$1,133.30