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	$169.49	5.193%	$178.2916	$178.29	$178.30	$178.30
Purchase #2	$127.78	6.512%	$136.101	$136.10	$136.10	$136.10
Purchase #3	$65.89	11.831%	$73.6854	$73.69	$73.70	$73.70
Purchase #4	$54.48	12.439%	$61.2568	$61.26	$61.25	$61.30
Purchase #5	$124.62	5.476%	$131.4442	$131.44	$131.45	$131.40
Purchase #6	$38.93	6.179%	$41.3355	$41.34	$41.35	$41.30
Purchase #7	$240.87	5.240%	$253.4916	$253.49	$253.50	$253.50
7 purchase totals =	$822.06		$875.6061	$875.61	$875.65	$875.60