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	$85.34	9.742%	$93.6538	$93.65	$93.65	$93.70
Purchase #2	$79.87	9.153%	$87.1805	$87.18	$87.20	$87.20
Purchase #3	$66.84	8.232%	$72.3423	$72.34	$72.35	$72.30
Purchase #4	$53.44	11.274%	$59.4648	$59.46	$59.45	$59.50
Purchase #5	$204.84	12.611%	$230.6724	$230.67	$230.65	$230.70
Purchase #6	$231.91	5.287%	$244.1711	$244.17	$244.15	$244.20
Purchase #7	$37.81	13.448%	$42.8947	$42.89	$42.90	$42.90
7 purchase totals =	$760.05		$830.3796	$830.36	$830.35	$830.50