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	$215.70	10.219%	$237.7424	$237.74	$237.75	$237.70
Purchase #2	$151.72	11.308%	$168.8765	$168.88	$168.90	$168.90
Purchase #3	$250.27	11.502%	$279.0561	$279.06	$279.05	$279.10
Purchase #4	$28.89	9.399%	$31.6054	$31.61	$31.60	$31.60
Purchase #5	$36.67	13.821%	$41.7382	$41.74	$41.75	$41.70
Purchase #6	$33.29	11.848%	$37.2342	$37.23	$37.25	$37.20
Purchase #7	$248.61	10.113%	$273.7519	$273.75	$273.75	$273.80
7 purchase totals =	$965.15		$1,070.0047	$1,070.01	$1,070.05	$1,070.00