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	$35.94	4.623%	$37.6015	$37.60	$37.60	$37.60
Purchase #2	$47.93	5.701%	$50.6625	$50.66	$50.65	$50.70
Purchase #3	$78.65	5.506%	$82.9805	$82.98	$83.00	$83.00
Purchase #4	$153.67	11.476%	$171.3052	$171.31	$171.30	$171.30
Purchase #5	$141.39	13.110%	$159.9262	$159.93	$159.95	$159.90
Purchase #6	$9.32	9.131%	$10.171	$10.17	$10.15	$10.20
Purchase #7	$233.73	12.824%	$263.7035	$263.70	$263.70	$263.70
7 purchase totals =	$700.63		$776.3504	$776.35	$776.35	$776.40