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	$165.33	6.105%	$175.4234	$175.42	$175.40	$175.40
Purchase #2	$208.33	10.214%	$229.6088	$229.61	$229.60	$229.60
Purchase #3	$138.75	12.636%	$156.2825	$156.28	$156.30	$156.30
Purchase #4	$143.56	5.801%	$151.8879	$151.89	$151.90	$151.90
Purchase #5	$44.94	9.541%	$49.2277	$49.23	$49.25	$49.20
Purchase #6	$213.78	4.682%	$223.7892	$223.79	$223.80	$223.80
Purchase #7	$95.52	11.299%	$106.3128	$106.31	$106.30	$106.30
7 purchase totals =	$1,010.21		$1,092.5323	$1,092.53	$1,092.55	$1,092.50