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	$100.46	10.482%	$110.9902	$110.99	$111.00	$111.00
Purchase #2	$110.28	10.174%	$121.4999	$121.50	$121.50	$121.50
Purchase #3	$32.50	7.839%	$35.0477	$35.05	$35.05	$35.00
Purchase #4	$98.76	11.589%	$110.2053	$110.21	$110.20	$110.20
Purchase #5	$52.46	3.822%	$54.465	$54.47	$54.45	$54.50
Purchase #6	$52.65	3.435%	$54.4585	$54.46	$54.45	$54.50
Purchase #7	$179.57	6.250%	$190.7931	$190.79	$190.80	$190.80
7 purchase totals =	$626.68		$677.4597	$677.47	$677.45	$677.50