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	$38.30	8.415%	$41.5229	$41.52	$41.50	$41.50
Purchase #2	$176.68	10.627%	$195.4558	$195.46	$195.45	$195.50
Purchase #3	$147.41	5.210%	$155.0901	$155.09	$155.10	$155.10
Purchase #4	$128.91	5.695%	$136.2514	$136.25	$136.25	$136.30
Purchase #5	$62.56	8.244%	$67.7174	$67.72	$67.70	$67.70
Purchase #6	$213.31	4.755%	$223.4529	$223.45	$223.45	$223.50
Purchase #7	$32.95	6.154%	$34.9777	$34.98	$35.00	$35.00
7 purchase totals =	$800.12		$854.4682	$854.47	$854.45	$854.60