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	$61.36	10.624%	$67.8789	$67.88	$67.90	$67.90
Purchase #2	$171.95	5.341%	$181.1338	$181.13	$181.15	$181.10
Purchase #3	$12.70	6.323%	$13.503	$13.50	$13.50	$13.50
Purchase #4	$115.33	13.391%	$130.7738	$130.77	$130.75	$130.80
Purchase #5	$133.70	5.752%	$141.3904	$141.39	$141.40	$141.40
Purchase #6	$179.75	4.283%	$187.4487	$187.45	$187.45	$187.40
Purchase #7	$61.57	6.144%	$65.3529	$65.35	$65.35	$65.40
7 purchase totals =	$736.36		$787.4815	$787.47	$787.50	$787.50