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	$201.77	13.418%	$228.8435	$228.84	$228.85	$228.80
Purchase #2	$77.93	8.638%	$84.6616	$84.66	$84.65	$84.70
Purchase #3	$223.35	4.522%	$233.4499	$233.45	$233.45	$233.40
Purchase #4	$94.86	3.678%	$98.349	$98.35	$98.35	$98.30
Purchase #5	$211.31	8.323%	$228.8973	$228.90	$228.90	$228.90
Purchase #6	$94.31	6.365%	$100.3128	$100.31	$100.30	$100.30
Purchase #7	$65.92	8.874%	$71.7697	$71.77	$71.75	$71.80
7 purchase totals =	$969.45		$1,046.2838	$1,046.28	$1,046.25	$1,046.20