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	$187.95	12.182%	$210.8461	$210.85	$210.85	$210.80
Purchase #2	$46.97	6.717%	$50.125	$50.13	$50.15	$50.10
Purchase #3	$85.49	4.630%	$89.4482	$89.45	$89.45	$89.40
Purchase #4	$222.44	9.361%	$243.2626	$243.26	$243.25	$243.30
Purchase #5	$87.67	3.379%	$90.6324	$90.63	$90.65	$90.60
Purchase #6	$108.93	3.648%	$112.9038	$112.90	$112.90	$112.90
Purchase #7	$84.37	12.234%	$94.6918	$94.69	$94.70	$94.70
7 purchase totals =	$823.82		$891.9099	$891.91	$891.95	$891.80