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	$45.90	10.192%	$50.5781	$50.58	$50.60	$50.60
Purchase #2	$38.46	13.351%	$43.5948	$43.59	$43.60	$43.60
Purchase #3	$97.63	6.628%	$104.1009	$104.10	$104.10	$104.10
Purchase #4	$106.51	6.713%	$113.66	$113.66	$113.65	$113.70
Purchase #5	$61.62	6.666%	$65.7276	$65.73	$65.75	$65.70
Purchase #6	$55.95	9.632%	$61.3391	$61.34	$61.35	$61.30
Purchase #7	$243.59	5.131%	$256.0886	$256.09	$256.10	$256.10
7 purchase totals =	$649.66		$695.0891	$695.09	$695.15	$695.10