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	$55.96	10.164%	$61.6478	$61.65	$61.65	$61.60
Purchase #2	$109.47	12.547%	$123.2052	$123.21	$123.20	$123.20
Purchase #3	$93.94	4.681%	$98.3373	$98.34	$98.35	$98.30
Purchase #4	$74.46	9.555%	$81.5747	$81.57	$81.55	$81.60
Purchase #5	$127.77	4.520%	$133.5452	$133.55	$133.55	$133.50
Purchase #6	$89.46	12.330%	$100.4904	$100.49	$100.50	$100.50
Purchase #7	$102.45	9.225%	$111.901	$111.90	$111.90	$111.90
7 purchase totals =	$653.51		$710.7016	$710.71	$710.70	$710.60