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	$174.66	9.649%	$191.5129	$191.51	$191.50	$191.50
Purchase #2	$128.27	13.475%	$145.5544	$145.55	$145.55	$145.60
Purchase #3	$149.37	12.530%	$168.0861	$168.09	$168.10	$168.10
Purchase #4	$212.37	8.529%	$230.483	$230.48	$230.50	$230.50
Purchase #5	$224.61	11.338%	$250.0763	$250.08	$250.10	$250.10
Purchase #6	$76.42	8.831%	$83.1687	$83.17	$83.15	$83.20
Purchase #7	$88.44	13.632%	$100.4961	$100.50	$100.50	$100.50
7 purchase totals =	$1,054.14		$1,169.3775	$1,169.38	$1,169.40	$1,169.50