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	$222.98	12.538%	$250.9372	$250.94	$250.95	$250.90
Purchase #2	$223.71	8.545%	$242.826	$242.83	$242.85	$242.80
Purchase #3	$40.67	3.151%	$41.9515	$41.95	$41.95	$42.00
Purchase #4	$200.70	10.779%	$222.3335	$222.33	$222.35	$222.30
Purchase #5	$7.29	10.867%	$8.0822	$8.08	$8.10	$8.10
Purchase #6	$153.73	11.258%	$171.0369	$171.04	$171.05	$171.00
Purchase #7	$70.90	11.306%	$78.916	$78.92	$78.90	$78.90
7 purchase totals =	$919.98		$1,016.0833	$1,016.09	$1,016.15	$1,016.00