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	$217.78	12.765%	$245.5796	$245.58	$245.60	$245.60
Purchase #2	$66.69	8.312%	$72.2333	$72.23	$72.25	$72.20
Purchase #3	$223.37	3.572%	$231.3488	$231.35	$231.35	$231.30
Purchase #4	$157.46	13.677%	$178.9958	$179.00	$179.00	$179.00
Purchase #5	$53.32	11.345%	$59.3692	$59.37	$59.35	$59.40
Purchase #6	$43.28	7.717%	$46.6199	$46.62	$46.60	$46.60
Purchase #7	$145.89	12.326%	$163.8724	$163.87	$163.85	$163.90
7 purchase totals =	$907.79		$998.0190	$998.02	$998.00	$998.00