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	$215.28	3.819%	$223.5015	$223.50	$223.50	$223.50
Purchase #2	$172.67	11.166%	$191.9503	$191.95	$191.95	$192.00
Purchase #3	$95.92	10.381%	$105.8775	$105.88	$105.90	$105.90
Purchase #4	$195.97	13.180%	$221.7988	$221.80	$221.80	$221.80
Purchase #5	$96.31	5.674%	$101.7746	$101.77	$101.75	$101.80
Purchase #6	$182.49	4.278%	$190.2969	$190.30	$190.30	$190.30
Purchase #7	$143.29	9.391%	$156.7464	$156.75	$156.75	$156.70
7 purchase totals =	$1,101.93		$1,191.9460	$1,191.95	$1,191.95	$1,192.00