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	$195.81	7.599%	$210.6896	$210.69	$210.70	$210.70
Purchase #2	$56.80	4.484%	$59.3469	$59.35	$59.35	$59.30
Purchase #3	$35.49	9.563%	$38.8839	$38.88	$38.90	$38.90
Purchase #4	$19.87	8.793%	$21.6172	$21.62	$21.60	$21.60
Purchase #5	$220.36	10.251%	$242.9491	$242.95	$242.95	$242.90
Purchase #6	$224.90	12.551%	$253.1272	$253.13	$253.15	$253.10
Purchase #7	$248.67	12.131%	$278.8362	$278.84	$278.85	$278.80
7 purchase totals =	$1,001.90		$1,105.4501	$1,105.46	$1,105.50	$1,105.30