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	$120.93	7.306%	$129.7651	$129.77	$129.75	$129.80
Purchase #2	$10.47	3.585%	$10.8453	$10.85	$10.85	$10.80
Purchase #3	$170.78	9.195%	$186.4832	$186.48	$186.50	$186.50
Purchase #4	$225.70	5.700%	$238.5649	$238.56	$238.55	$238.60
Purchase #5	$184.72	7.399%	$198.3874	$198.39	$198.40	$198.40
Purchase #6	$131.70	4.415%	$137.5146	$137.51	$137.50	$137.50
Purchase #7	$146.88	12.530%	$165.2841	$165.28	$165.30	$165.30
7 purchase totals =	$991.18		$1,066.8446	$1,066.84	$1,066.85	$1,066.90