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	$223.89	9.610%	$245.4058	$245.41	$245.40	$245.40
Purchase #2	$173.95	3.773%	$180.5131	$180.51	$180.50	$180.50
Purchase #3	$162.89	5.864%	$172.4419	$172.44	$172.45	$172.40
Purchase #4	$159.30	13.358%	$180.5793	$180.58	$180.60	$180.60
Purchase #5	$26.65	5.468%	$28.1072	$28.11	$28.10	$28.10
Purchase #6	$80.63	12.349%	$90.587	$90.59	$90.60	$90.60
Purchase #7	$52.87	10.168%	$58.2458	$58.25	$58.25	$58.20
7 purchase totals =	$880.18		$955.8801	$955.89	$955.90	$955.80