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	$174.90	9.313%	$191.1884	$191.19	$191.20	$191.20
Purchase #2	$172.83	13.194%	$195.6332	$195.63	$195.65	$195.60
Purchase #3	$137.39	9.519%	$150.4682	$150.47	$150.45	$150.50
Purchase #4	$96.65	4.291%	$100.7973	$100.80	$100.80	$100.80
Purchase #5	$80.77	5.644%	$85.3287	$85.33	$85.35	$85.30
Purchase #6	$98.66	8.412%	$106.9593	$106.96	$106.95	$107.00
Purchase #7	$55.46	6.476%	$59.0516	$59.05	$59.05	$59.10
7 purchase totals =	$816.66		$889.4267	$889.43	$889.45	$889.50