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	$185.60	12.535%	$208.865	$208.87	$208.85	$208.90
Purchase #2	$250.51	3.645%	$259.6411	$259.64	$259.65	$259.60
Purchase #3	$247.77	9.319%	$270.8597	$270.86	$270.85	$270.90
Purchase #4	$40.49	5.121%	$42.5635	$42.56	$42.55	$42.60
Purchase #5	$181.92	10.240%	$200.5486	$200.55	$200.55	$200.50
Purchase #6	$177.90	13.128%	$201.2547	$201.25	$201.25	$201.30
Purchase #7	$89.25	3.218%	$92.1221	$92.12	$92.10	$92.10
7 purchase totals =	$1,173.44		$1,275.8547	$1,275.85	$1,275.80	$1,275.90