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	$133.47	13.267%	$151.1775	$151.18	$151.20	$151.20
Purchase #2	$86.98	5.616%	$91.8648	$91.86	$91.85	$91.90
Purchase #3	$42.53	10.176%	$46.8579	$46.86	$46.85	$46.90
Purchase #4	$115.95	10.323%	$127.9195	$127.92	$127.90	$127.90
Purchase #5	$232.63	13.860%	$264.8725	$264.87	$264.85	$264.90
Purchase #6	$249.35	4.350%	$260.1967	$260.20	$260.20	$260.20
Purchase #7	$203.46	13.819%	$231.5761	$231.58	$231.60	$231.60
7 purchase totals =	$1,064.37		$1,174.4650	$1,174.47	$1,174.45	$1,174.60