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	$50.83	4.750%	$53.2444	$53.24	$53.25	$53.20
Purchase #2	$27.29	13.198%	$30.8917	$30.89	$30.90	$30.90
Purchase #3	$64.43	12.420%	$72.4322	$72.43	$72.45	$72.40
Purchase #4	$231.69	8.224%	$250.7442	$250.74	$250.75	$250.70
Purchase #5	$143.75	7.436%	$154.4393	$154.44	$154.45	$154.40
Purchase #6	$144.54	6.428%	$153.831	$153.83	$153.85	$153.80
Purchase #7	$151.57	13.125%	$171.4636	$171.46	$171.45	$171.50
7 purchase totals =	$814.10		$887.0464	$887.03	$887.10	$886.90