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	$87.48	13.681%	$99.4481	$99.45	$99.45	$99.40
Purchase #2	$196.97	11.360%	$219.3458	$219.35	$219.35	$219.30
Purchase #3	$71.84	13.856%	$81.7942	$81.79	$81.80	$81.80
Purchase #4	$35.69	7.823%	$38.482	$38.48	$38.50	$38.50
Purchase #5	$209.91	3.288%	$216.8118	$216.81	$216.80	$216.80
Purchase #6	$81.59	11.422%	$90.9092	$90.91	$90.90	$90.90
Purchase #7	$141.75	6.817%	$151.4131	$151.41	$151.40	$151.40
7 purchase totals =	$825.23		$898.2042	$898.20	$898.20	$898.10