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	$67.62	8.527%	$73.386	$73.39	$73.40	$73.40
Purchase #2	$95.58	10.870%	$105.9695	$105.97	$105.95	$106.00
Purchase #3	$124.47	5.468%	$131.276	$131.28	$131.30	$131.30
Purchase #4	$45.27	11.597%	$50.52	$50.52	$50.50	$50.50
Purchase #5	$89.93	10.122%	$99.0327	$99.03	$99.05	$99.00
Purchase #6	$144.73	6.491%	$154.1244	$154.12	$154.10	$154.10
Purchase #7	$208.53	10.873%	$231.2035	$231.20	$231.20	$231.20
7 purchase totals =	$776.13		$845.5121	$845.51	$845.50	$845.50