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	$32.37	8.629%	$35.1632	$35.16	$35.15	$35.20
Purchase #2	$225.92	13.663%	$256.7874	$256.79	$256.80	$256.80
Purchase #3	$90.78	8.420%	$98.4237	$98.42	$98.40	$98.40
Purchase #4	$104.46	10.683%	$115.6195	$115.62	$115.60	$115.60
Purchase #5	$140.48	8.579%	$152.5318	$152.53	$152.55	$152.50
Purchase #6	$184.41	10.570%	$203.9021	$203.90	$203.90	$203.90
Purchase #7	$218.86	11.234%	$243.4467	$243.45	$243.45	$243.40
7 purchase totals =	$997.28		$1,105.8744	$1,105.87	$1,105.85	$1,105.80