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	$145.78	3.334%	$150.6403	$150.64	$150.65	$150.60
Purchase #2	$227.45	9.704%	$249.5217	$249.52	$249.50	$249.50
Purchase #3	$68.66	12.350%	$77.1395	$77.14	$77.15	$77.10
Purchase #4	$154.69	12.207%	$173.573	$173.57	$173.55	$173.60
Purchase #5	$65.58	8.146%	$70.9221	$70.92	$70.90	$70.90
Purchase #6	$155.50	4.192%	$162.0186	$162.02	$162.00	$162.00
Purchase #7	$174.65	7.334%	$187.4588	$187.46	$187.45	$187.50
7 purchase totals =	$992.31		$1,071.2740	$1,071.27	$1,071.20	$1,071.20