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	$94.67	11.557%	$105.611	$105.61	$105.60	$105.60
Purchase #2	$95.61	6.432%	$101.7596	$101.76	$101.75	$101.80
Purchase #3	$210.73	5.592%	$222.514	$222.51	$222.50	$222.50
Purchase #4	$35.99	13.562%	$40.871	$40.87	$40.85	$40.90
Purchase #5	$58.87	10.566%	$65.0902	$65.09	$65.10	$65.10
Purchase #6	$122.55	7.521%	$131.767	$131.77	$131.75	$131.80
Purchase #7	$226.53	12.478%	$254.7964	$254.80	$254.80	$254.80
7 purchase totals =	$844.95		$922.4092	$922.41	$922.35	$922.50