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	$115.37	7.378%	$123.882	$123.88	$123.90	$123.90
Purchase #2	$17.80	6.553%	$18.9664	$18.97	$18.95	$19.00
Purchase #3	$243.54	4.168%	$253.6907	$253.69	$253.70	$253.70
Purchase #4	$67.39	10.776%	$74.6519	$74.65	$74.65	$74.70
Purchase #5	$93.91	5.256%	$98.8459	$98.85	$98.85	$98.80
Purchase #6	$160.31	5.697%	$169.4429	$169.44	$169.45	$169.40
Purchase #7	$105.28	6.205%	$111.8126	$111.81	$111.80	$111.80
7 purchase totals =	$803.60		$851.2924	$851.29	$851.30	$851.30