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	$82.82	10.466%	$91.4879	$91.49	$91.50	$91.50
Purchase #2	$186.35	13.581%	$211.6582	$211.66	$211.65	$211.70
Purchase #3	$36.48	12.743%	$41.1286	$41.13	$41.15	$41.10
Purchase #4	$160.83	5.384%	$169.4891	$169.49	$169.50	$169.50
Purchase #5	$110.28	8.360%	$119.4994	$119.50	$119.50	$119.50
Purchase #6	$77.27	11.718%	$86.3245	$86.32	$86.30	$86.30
Purchase #7	$25.79	7.521%	$27.7297	$27.73	$27.75	$27.70
7 purchase totals =	$679.82		$747.3174	$747.32	$747.35	$747.30