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	$49.73	11.814%	$55.6051	$55.61	$55.60	$55.60
Purchase #2	$241.30	12.392%	$271.2019	$271.20	$271.20	$271.20
Purchase #3	$151.34	9.365%	$165.513	$165.51	$165.50	$165.50
Purchase #4	$135.35	13.474%	$153.5871	$153.59	$153.60	$153.60
Purchase #5	$135.81	12.257%	$152.4562	$152.46	$152.45	$152.50
Purchase #6	$198.40	11.451%	$221.1188	$221.12	$221.10	$221.10
Purchase #7	$134.55	12.562%	$151.4522	$151.45	$151.45	$151.50
7 purchase totals =	$1,046.48		$1,170.9343	$1,170.94	$1,170.90	$1,171.00