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	$57.64	10.234%	$63.5389	$63.54	$63.55	$63.50
Purchase #2	$91.38	10.427%	$100.9082	$100.91	$100.90	$100.90
Purchase #3	$190.66	4.849%	$199.9051	$199.91	$199.90	$199.90
Purchase #4	$35.48	7.434%	$38.1176	$38.12	$38.10	$38.10
Purchase #5	$80.26	8.261%	$86.8903	$86.89	$86.90	$86.90
Purchase #6	$240.27	13.386%	$272.4325	$272.43	$272.45	$272.40
Purchase #7	$99.55	7.654%	$107.1696	$107.17	$107.15	$107.20
7 purchase totals =	$795.24		$868.9622	$868.97	$868.95	$868.90