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	$58.44	4.122%	$60.8489	$60.85	$60.85	$60.80
Purchase #2	$188.33	11.691%	$210.3477	$210.35	$210.35	$210.30
Purchase #3	$89.63	3.410%	$92.6864	$92.69	$92.70	$92.70
Purchase #4	$188.72	12.808%	$212.8913	$212.89	$212.90	$212.90
Purchase #5	$32.40	3.545%	$33.5486	$33.55	$33.55	$33.50
Purchase #6	$197.97	12.297%	$222.3144	$222.31	$222.30	$222.30
Purchase #7	$121.99	7.763%	$131.4601	$131.46	$131.45	$131.50
7 purchase totals =	$877.48		$964.0974	$964.10	$964.10	$964.00