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	$63.40	3.838%	$65.8333	$65.83	$65.85	$65.80
Purchase #2	$143.72	4.597%	$150.3268	$150.33	$150.35	$150.30
Purchase #3	$67.31	5.361%	$70.9185	$70.92	$70.90	$70.90
Purchase #4	$94.99	4.328%	$99.1012	$99.10	$99.10	$99.10
Purchase #5	$167.62	10.431%	$185.1044	$185.10	$185.10	$185.10
Purchase #6	$84.31	12.798%	$95.1	$95.10	$95.10	$95.10
Purchase #7	$186.29	7.267%	$199.8277	$199.83	$199.85	$199.80
7 purchase totals =	$807.64		$866.2119	$866.21	$866.25	$866.10