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	$97.43	4.600%	$101.9118	$101.91	$101.90	$101.90
Purchase #2	$133.61	4.560%	$139.7026	$139.70	$139.70	$139.70
Purchase #3	$67.40	5.843%	$71.3382	$71.34	$71.35	$71.30
Purchase #4	$160.62	11.833%	$179.6262	$179.63	$179.65	$179.60
Purchase #5	$161.39	6.798%	$172.3613	$172.36	$172.35	$172.40
Purchase #6	$244.95	13.559%	$278.1628	$278.16	$278.15	$278.20
Purchase #7	$84.86	6.652%	$90.5049	$90.50	$90.50	$90.50
7 purchase totals =	$950.26		$1,033.6078	$1,033.60	$1,033.60	$1,033.60