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	$7.30	4.569%	$7.6335	$7.63	$7.65	$7.60
Purchase #2	$243.81	10.760%	$270.044	$270.04	$270.05	$270.00
Purchase #3	$31.86	10.297%	$35.1406	$35.14	$35.15	$35.10
Purchase #4	$94.58	11.631%	$105.5806	$105.58	$105.60	$105.60
Purchase #5	$38.68	3.693%	$40.1085	$40.11	$40.10	$40.10
Purchase #6	$215.53	11.597%	$240.525	$240.53	$240.55	$240.50
Purchase #7	$153.83	10.288%	$169.656	$169.66	$169.65	$169.70
7 purchase totals =	$785.59		$868.6882	$868.69	$868.75	$868.60