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	$61.60	9.375%	$67.375	$67.38	$67.40	$67.40
Purchase #2	$31.38	10.756%	$34.7552	$34.76	$34.75	$34.80
Purchase #3	$205.58	8.288%	$222.6185	$222.62	$222.60	$222.60
Purchase #4	$117.59	9.353%	$128.5882	$128.59	$128.60	$128.60
Purchase #5	$250.95	13.183%	$284.0327	$284.03	$284.05	$284.00
Purchase #6	$59.45	6.187%	$63.1282	$63.13	$63.15	$63.10
Purchase #7	$180.90	10.131%	$199.227	$199.23	$199.25	$199.20
7 purchase totals =	$907.45		$999.7248	$999.74	$999.80	$999.70