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	$35.82	3.356%	$37.0221	$37.02	$37.00	$37.00
Purchase #2	$87.88	3.127%	$90.628	$90.63	$90.65	$90.60
Purchase #3	$113.85	11.760%	$127.2388	$127.24	$127.25	$127.20
Purchase #4	$6.37	9.348%	$6.9655	$6.97	$6.95	$7.00
Purchase #5	$56.41	11.388%	$62.834	$62.83	$62.85	$62.80
Purchase #6	$177.62	11.692%	$198.3873	$198.39	$198.40	$198.40
Purchase #7	$42.80	12.530%	$48.1628	$48.16	$48.15	$48.20
7 purchase totals =	$520.75		$571.2385	$571.24	$571.25	$571.20