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	$143.63	8.803%	$156.2737	$156.27	$156.25	$156.30
Purchase #2	$165.53	12.170%	$185.675	$185.68	$185.70	$185.70
Purchase #3	$201.92	4.707%	$211.4244	$211.42	$211.40	$211.40
Purchase #4	$197.83	12.482%	$222.5231	$222.52	$222.50	$222.50
Purchase #5	$126.46	3.726%	$131.1719	$131.17	$131.15	$131.20
Purchase #6	$66.45	12.522%	$74.7709	$74.77	$74.75	$74.80
Purchase #7	$171.46	9.336%	$187.4675	$187.47	$187.45	$187.50
7 purchase totals =	$1,073.28		$1,169.3065	$1,169.30	$1,169.20	$1,169.40