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	$139.30	6.613%	$148.5119	$148.51	$148.50	$148.50
Purchase #2	$197.55	6.496%	$210.3828	$210.38	$210.40	$210.40
Purchase #3	$53.25	5.169%	$56.0025	$56.00	$56.00	$56.00
Purchase #4	$74.50	5.232%	$78.3978	$78.40	$78.40	$78.40
Purchase #5	$165.26	11.451%	$184.1839	$184.18	$184.20	$184.20
Purchase #6	$34.25	11.601%	$38.2233	$38.22	$38.20	$38.20
Purchase #7	$31.54	7.383%	$33.8686	$33.87	$33.85	$33.90
7 purchase totals =	$695.65		$749.5708	$749.56	$749.55	$749.60