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	$86.67	9.802%	$95.1654	$95.17	$95.15	$95.20
Purchase #2	$52.78	3.143%	$54.4389	$54.44	$54.45	$54.40
Purchase #3	$6.85	4.356%	$7.1484	$7.15	$7.15	$7.10
Purchase #4	$108.33	9.652%	$118.786	$118.79	$118.80	$118.80
Purchase #5	$131.70	10.826%	$145.9578	$145.96	$145.95	$146.00
Purchase #6	$54.69	12.107%	$61.3113	$61.31	$61.30	$61.30
Purchase #7	$26.61	4.874%	$27.907	$27.91	$27.90	$27.90
7 purchase totals =	$467.63		$510.7148	$510.73	$510.70	$510.70