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	$59.87	13.214%	$67.7812	$67.78	$67.80	$67.80
Purchase #2	$48.67	7.696%	$52.4156	$52.42	$52.40	$52.40
Purchase #3	$209.84	9.490%	$229.7538	$229.75	$229.75	$229.80
Purchase #4	$57.26	7.386%	$61.4892	$61.49	$61.50	$61.50
Purchase #5	$199.97	5.550%	$211.0683	$211.07	$211.05	$211.10
Purchase #6	$152.41	8.627%	$165.5584	$165.56	$165.55	$165.60
Purchase #7	$197.56	12.802%	$222.8516	$222.85	$222.85	$222.90
7 purchase totals =	$925.58		$1,010.9181	$1,010.92	$1,010.90	$1,011.10