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	$118.60	11.628%	$132.3908	$132.39	$132.40	$132.40
Purchase #2	$39.60	4.829%	$41.5123	$41.51	$41.50	$41.50
Purchase #3	$35.51	3.660%	$36.8097	$36.81	$36.80	$36.80
Purchase #4	$32.47	13.642%	$36.8996	$36.90	$36.90	$36.90
Purchase #5	$229.76	5.685%	$242.8219	$242.82	$242.80	$242.80
Purchase #6	$173.96	11.651%	$194.2281	$194.23	$194.25	$194.20
Purchase #7	$18.98	11.560%	$21.1741	$21.17	$21.15	$21.20
7 purchase totals =	$648.88		$705.8365	$705.83	$705.80	$705.80