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	$35.41	9.545%	$38.7899	$38.79	$38.80	$38.80
Purchase #2	$82.68	4.131%	$86.0955	$86.10	$86.10	$86.10
Purchase #3	$226.66	6.335%	$241.0189	$241.02	$241.00	$241.00
Purchase #4	$219.89	4.535%	$229.862	$229.86	$229.85	$229.90
Purchase #5	$154.57	6.864%	$165.1797	$165.18	$165.20	$165.20
Purchase #6	$146.33	3.678%	$151.712	$151.71	$151.70	$151.70
Purchase #7	$153.83	4.539%	$160.8123	$160.81	$160.80	$160.80
7 purchase totals =	$1,019.37		$1,073.4703	$1,073.47	$1,073.45	$1,073.50