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	$42.33	13.167%	$47.9036	$47.90	$47.90	$47.90
Purchase #2	$200.28	11.221%	$222.7534	$222.75	$222.75	$222.80
Purchase #3	$244.75	11.214%	$272.1963	$272.20	$272.20	$272.20
Purchase #4	$54.41	12.165%	$61.029	$61.03	$61.05	$61.00
Purchase #5	$57.72	3.467%	$59.7212	$59.72	$59.70	$59.70
Purchase #6	$179.41	13.641%	$203.8833	$203.88	$203.90	$203.90
Purchase #7	$89.66	11.289%	$99.7817	$99.78	$99.80	$99.80
7 purchase totals =	$868.56		$967.2685	$967.26	$967.30	$967.30