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	$193.89	8.503%	$210.3765	$210.38	$210.40	$210.40
Purchase #2	$26.73	6.818%	$28.5525	$28.55	$28.55	$28.60
Purchase #3	$239.25	6.783%	$255.4783	$255.48	$255.50	$255.50
Purchase #4	$232.58	13.549%	$264.0923	$264.09	$264.10	$264.10
Purchase #5	$146.95	8.606%	$159.5965	$159.60	$159.60	$159.60
Purchase #6	$40.56	11.782%	$45.3388	$45.34	$45.35	$45.30
Purchase #7	$232.91	13.473%	$264.29	$264.29	$264.30	$264.30
7 purchase totals =	$1,112.87		$1,227.7249	$1,227.73	$1,227.80	$1,227.80