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	$35.47	6.716%	$37.8522	$37.85	$37.85	$37.90
Purchase #2	$100.87	11.333%	$112.3016	$112.30	$112.30	$112.30
Purchase #3	$10.86	12.140%	$12.1784	$12.18	$12.20	$12.20
Purchase #4	$125.57	13.739%	$142.8221	$142.82	$142.80	$142.80
Purchase #5	$83.68	8.234%	$90.5702	$90.57	$90.55	$90.60
Purchase #6	$180.99	7.568%	$194.6873	$194.69	$194.70	$194.70
Purchase #7	$99.39	13.387%	$112.6953	$112.70	$112.70	$112.70
7 purchase totals =	$636.83		$703.1071	$703.11	$703.10	$703.20