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	$48.97	8.521%	$53.1427	$53.14	$53.15	$53.10
Purchase #2	$179.96	11.356%	$200.3963	$200.40	$200.40	$200.40
Purchase #3	$48.75	4.103%	$50.7502	$50.75	$50.75	$50.80
Purchase #4	$95.70	12.502%	$107.6644	$107.66	$107.65	$107.70
Purchase #5	$232.99	12.288%	$261.6198	$261.62	$261.60	$261.60
Purchase #6	$168.27	13.142%	$190.384	$190.38	$190.40	$190.40
Purchase #7	$128.40	8.629%	$139.4796	$139.48	$139.50	$139.50
7 purchase totals =	$903.04		$1,003.4370	$1,003.43	$1,003.45	$1,003.50