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	$89.33	9.114%	$97.4715	$97.47	$97.45	$97.50
Purchase #2	$143.44	6.519%	$152.7909	$152.79	$152.80	$152.80
Purchase #3	$95.83	6.114%	$101.689	$101.69	$101.70	$101.70
Purchase #4	$222.89	3.397%	$230.4616	$230.46	$230.45	$230.50
Purchase #5	$114.63	7.722%	$123.4817	$123.48	$123.50	$123.50
Purchase #6	$63.68	3.709%	$66.0419	$66.04	$66.05	$66.00
Purchase #7	$247.90	9.123%	$270.5159	$270.52	$270.50	$270.50
7 purchase totals =	$977.70		$1,042.4525	$1,042.45	$1,042.45	$1,042.50