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	$169.48	7.202%	$181.6859	$181.69	$181.70	$181.70
Purchase #2	$77.98	7.221%	$83.6109	$83.61	$83.60	$83.60
Purchase #3	$199.87	13.445%	$226.7425	$226.74	$226.75	$226.70
Purchase #4	$11.27	5.627%	$11.9042	$11.90	$11.90	$11.90
Purchase #5	$249.58	11.621%	$278.5837	$278.58	$278.60	$278.60
Purchase #6	$134.53	8.160%	$145.5076	$145.51	$145.50	$145.50
Purchase #7	$137.46	4.437%	$143.5591	$143.56	$143.55	$143.60
7 purchase totals =	$980.17		$1,071.5939	$1,071.59	$1,071.60	$1,071.60