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	$60.61	11.675%	$67.6862	$67.69	$67.70	$67.70
Purchase #2	$150.97	6.206%	$160.3392	$160.34	$160.35	$160.30
Purchase #3	$35.50	4.548%	$37.1145	$37.11	$37.10	$37.10
Purchase #4	$136.82	13.183%	$154.857	$154.86	$154.85	$154.90
Purchase #5	$170.63	6.211%	$181.2278	$181.23	$181.25	$181.20
Purchase #6	$94.62	7.240%	$101.4705	$101.47	$101.45	$101.50
Purchase #7	$102.72	8.177%	$111.1194	$111.12	$111.10	$111.10
7 purchase totals =	$751.87		$813.8146	$813.82	$813.80	$813.80