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	$100.56	7.620%	$108.2227	$108.22	$108.20	$108.20
Purchase #2	$126.78	8.125%	$137.0809	$137.08	$137.10	$137.10
Purchase #3	$82.91	6.647%	$88.421	$88.42	$88.40	$88.40
Purchase #4	$57.50	3.297%	$59.3958	$59.40	$59.40	$59.40
Purchase #5	$240.35	7.487%	$258.345	$258.35	$258.35	$258.30
Purchase #6	$62.69	13.506%	$71.1569	$71.16	$71.15	$71.20
Purchase #7	$56.51	12.596%	$63.628	$63.63	$63.65	$63.60
7 purchase totals =	$727.30		$786.2503	$786.26	$786.25	$786.20