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	$175.31	8.744%	$190.6391	$190.64	$190.65	$190.60
Purchase #2	$50.32	11.605%	$56.1596	$56.16	$56.15	$56.20
Purchase #3	$55.96	5.120%	$58.8252	$58.83	$58.85	$58.80
Purchase #4	$63.45	6.160%	$67.3585	$67.36	$67.35	$67.40
Purchase #5	$56.27	6.200%	$59.7587	$59.76	$59.75	$59.80
Purchase #6	$237.49	3.217%	$245.1301	$245.13	$245.15	$245.10
Purchase #7	$214.83	6.200%	$228.1495	$228.15	$228.15	$228.10
7 purchase totals =	$853.63		$906.0207	$906.03	$906.05	$906.00