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	$36.68	11.864%	$41.0317	$41.03	$41.05	$41.00
Purchase #2	$58.51	10.840%	$64.8525	$64.85	$64.85	$64.90
Purchase #3	$11.92	5.489%	$12.5743	$12.57	$12.55	$12.60
Purchase #4	$61.70	13.647%	$70.1202	$70.12	$70.10	$70.10
Purchase #5	$74.40	5.436%	$78.4444	$78.44	$78.45	$78.40
Purchase #6	$84.28	4.443%	$88.0246	$88.02	$88.00	$88.00
Purchase #7	$152.96	3.658%	$158.5553	$158.56	$158.55	$158.60
7 purchase totals =	$480.45		$513.6030	$513.59	$513.55	$513.60