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	$187.78	5.710%	$198.5022	$198.50	$198.50	$198.50
Purchase #2	$19.39	7.238%	$20.7934	$20.79	$20.80	$20.80
Purchase #3	$48.81	8.857%	$53.1331	$53.13	$53.15	$53.10
Purchase #4	$179.58	10.825%	$199.0195	$199.02	$199.00	$199.00
Purchase #5	$124.73	13.463%	$141.5224	$141.52	$141.50	$141.50
Purchase #6	$30.44	11.748%	$34.0161	$34.02	$34.00	$34.00
Purchase #7	$18.54	10.452%	$20.4778	$20.48	$20.50	$20.50
7 purchase totals =	$609.27		$667.4645	$667.46	$667.45	$667.40