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	$40.94	7.853%	$44.155	$44.16	$44.15	$44.20
Purchase #2	$126.92	9.836%	$139.4039	$139.40	$139.40	$139.40
Purchase #3	$25.82	4.694%	$27.032	$27.03	$27.05	$27.00
Purchase #4	$95.62	8.155%	$103.4178	$103.42	$103.40	$103.40
Purchase #5	$61.90	9.566%	$67.8214	$67.82	$67.80	$67.80
Purchase #6	$99.37	4.581%	$103.9221	$103.92	$103.90	$103.90
Purchase #7	$195.76	12.230%	$219.7014	$219.70	$219.70	$219.70
7 purchase totals =	$646.33		$705.4536	$705.45	$705.40	$705.40