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	$166.82	11.329%	$185.719	$185.72	$185.70	$185.70
Purchase #2	$38.76	5.743%	$40.986	$40.99	$41.00	$41.00
Purchase #3	$91.67	4.144%	$95.4688	$95.47	$95.45	$95.50
Purchase #4	$238.57	8.803%	$259.5713	$259.57	$259.55	$259.60
Purchase #5	$241.54	13.631%	$274.4643	$274.46	$274.45	$274.50
Purchase #6	$180.94	8.259%	$195.8838	$195.88	$195.90	$195.90
Purchase #7	$216.93	11.732%	$242.3802	$242.38	$242.40	$242.40
7 purchase totals =	$1,175.23		$1,294.4734	$1,294.47	$1,294.45	$1,294.60