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	$196.40	4.303%	$204.8511	$204.85	$204.85	$204.90
Purchase #2	$55.54	10.442%	$61.3395	$61.34	$61.35	$61.30
Purchase #3	$102.60	7.684%	$110.4838	$110.48	$110.50	$110.50
Purchase #4	$153.72	12.688%	$173.224	$173.22	$173.20	$173.20
Purchase #5	$182.34	3.231%	$188.2314	$188.23	$188.25	$188.20
Purchase #6	$153.60	9.467%	$168.1413	$168.14	$168.15	$168.10
Purchase #7	$160.49	3.691%	$166.4137	$166.41	$166.40	$166.40
7 purchase totals =	$1,004.69		$1,072.6848	$1,072.67	$1,072.70	$1,072.60