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	$162.80	13.803%	$185.2713	$185.27	$185.25	$185.30
Purchase #2	$43.56	3.871%	$45.2462	$45.25	$45.25	$45.20
Purchase #3	$76.85	12.114%	$86.1596	$86.16	$86.15	$86.20
Purchase #4	$31.50	5.552%	$33.2489	$33.25	$33.25	$33.20
Purchase #5	$193.63	10.195%	$213.3706	$213.37	$213.35	$213.40
Purchase #6	$238.88	7.329%	$256.3875	$256.39	$256.40	$256.40
Purchase #7	$155.95	8.817%	$169.7001	$169.70	$169.70	$169.70
7 purchase totals =	$903.17		$989.3842	$989.39	$989.35	$989.40