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	$247.66	8.811%	$269.4813	$269.48	$269.50	$269.50
Purchase #2	$27.94	4.290%	$29.1386	$29.14	$29.15	$29.10
Purchase #3	$196.37	7.580%	$211.2548	$211.25	$211.25	$211.30
Purchase #4	$58.52	6.538%	$62.346	$62.35	$62.35	$62.30
Purchase #5	$243.50	3.304%	$251.5452	$251.55	$251.55	$251.50
Purchase #6	$123.54	11.612%	$137.8855	$137.89	$137.90	$137.90
Purchase #7	$242.89	13.712%	$276.1951	$276.20	$276.20	$276.20
7 purchase totals =	$1,140.42		$1,237.8465	$1,237.86	$1,237.90	$1,237.80