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	$102.70	5.281%	$108.1236	$108.12	$108.10	$108.10
Purchase #2	$84.66	5.666%	$89.4568	$89.46	$89.45	$89.50
Purchase #3	$43.89	13.408%	$49.7748	$49.77	$49.75	$49.80
Purchase #4	$155.47	8.546%	$168.7565	$168.76	$168.75	$168.80
Purchase #5	$179.81	11.457%	$200.4108	$200.41	$200.40	$200.40
Purchase #6	$89.80	10.534%	$99.2595	$99.26	$99.25	$99.30
Purchase #7	$236.53	4.771%	$247.8148	$247.81	$247.80	$247.80
7 purchase totals =	$892.86		$963.5968	$963.59	$963.50	$963.70