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	$165.47	4.415%	$172.7755	$172.78	$172.80	$172.80
Purchase #2	$12.29	12.717%	$13.8529	$13.85	$13.85	$13.90
Purchase #3	$167.99	8.329%	$181.9819	$181.98	$182.00	$182.00
Purchase #4	$53.89	4.291%	$56.2024	$56.20	$56.20	$56.20
Purchase #5	$86.92	10.283%	$95.858	$95.86	$95.85	$95.90
Purchase #6	$147.90	13.518%	$167.8931	$167.89	$167.90	$167.90
Purchase #7	$39.43	8.864%	$42.9251	$42.93	$42.95	$42.90
7 purchase totals =	$673.89		$731.4889	$731.49	$731.55	$731.60