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	$118.55	9.755%	$130.1146	$130.11	$130.10	$130.10
Purchase #2	$147.98	13.171%	$167.4704	$167.47	$167.45	$167.50
Purchase #3	$104.77	13.137%	$118.5336	$118.53	$118.55	$118.50
Purchase #4	$176.29	13.386%	$199.8882	$199.89	$199.90	$199.90
Purchase #5	$137.51	11.333%	$153.094	$153.09	$153.10	$153.10
Purchase #6	$53.86	10.118%	$59.3096	$59.31	$59.30	$59.30
Purchase #7	$168.40	7.659%	$181.2978	$181.30	$181.30	$181.30
7 purchase totals =	$907.36		$1,009.7082	$1,009.70	$1,009.70	$1,009.70