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	$236.41	4.387%	$246.7813	$246.78	$246.80	$246.80
Purchase #2	$250.28	9.530%	$274.1317	$274.13	$274.15	$274.10
Purchase #3	$217.51	6.380%	$231.3871	$231.39	$231.40	$231.40
Purchase #4	$69.88	12.602%	$78.6863	$78.69	$78.70	$78.70
Purchase #5	$99.69	4.378%	$104.0544	$104.05	$104.05	$104.10
Purchase #6	$51.73	3.674%	$53.6306	$53.63	$53.65	$53.60
Purchase #7	$67.39	12.631%	$75.902	$75.90	$75.90	$75.90
7 purchase totals =	$992.89		$1,064.5734	$1,064.57	$1,064.65	$1,064.60