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	$243.39	8.839%	$264.9032	$264.90	$264.90	$264.90
Purchase #2	$80.87	3.167%	$83.4312	$83.43	$83.45	$83.40
Purchase #3	$109.86	10.346%	$121.2261	$121.23	$121.25	$121.20
Purchase #4	$180.54	10.815%	$200.0654	$200.07	$200.05	$200.10
Purchase #5	$236.45	4.372%	$246.7876	$246.79	$246.80	$246.80
Purchase #6	$60.59	3.572%	$62.7543	$62.75	$62.75	$62.80
Purchase #7	$122.73	3.199%	$126.6561	$126.66	$126.65	$126.70
7 purchase totals =	$1,034.43		$1,105.8239	$1,105.83	$1,105.85	$1,105.90