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	$226.67	10.510%	$250.493	$250.49	$250.50	$250.50
Purchase #2	$191.68	3.873%	$199.1038	$199.10	$199.10	$199.10
Purchase #3	$225.46	8.273%	$244.1123	$244.11	$244.10	$244.10
Purchase #4	$59.94	9.523%	$65.6481	$65.65	$65.65	$65.60
Purchase #5	$107.30	11.625%	$119.7736	$119.77	$119.75	$119.80
Purchase #6	$91.54	7.503%	$98.4082	$98.41	$98.40	$98.40
Purchase #7	$33.69	10.138%	$37.1055	$37.11	$37.10	$37.10
7 purchase totals =	$936.28		$1,014.6445	$1,014.64	$1,014.60	$1,014.60