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	$141.37	12.212%	$158.6341	$158.63	$158.65	$158.60
Purchase #2	$139.62	9.263%	$152.553	$152.55	$152.55	$152.60
Purchase #3	$158.45	5.817%	$167.667	$167.67	$167.65	$167.70
Purchase #4	$78.62	13.282%	$89.0623	$89.06	$89.05	$89.10
Purchase #5	$66.84	3.846%	$69.4107	$69.41	$69.40	$69.40
Purchase #6	$169.48	6.408%	$180.3403	$180.34	$180.35	$180.30
Purchase #7	$245.90	3.634%	$254.836	$254.84	$254.85	$254.80
7 purchase totals =	$1,000.28		$1,072.5034	$1,072.50	$1,072.50	$1,072.50