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	$59.82	7.466%	$64.2862	$64.29	$64.30	$64.30
Purchase #2	$89.92	12.192%	$100.883	$100.88	$100.90	$100.90
Purchase #3	$190.92	13.406%	$216.5147	$216.51	$216.50	$216.50
Purchase #4	$95.53	9.765%	$104.8585	$104.86	$104.85	$104.90
Purchase #5	$50.53	7.639%	$54.39	$54.39	$54.40	$54.40
Purchase #6	$174.97	5.586%	$184.7438	$184.74	$184.75	$184.70
Purchase #7	$132.56	13.273%	$150.1547	$150.15	$150.15	$150.20
7 purchase totals =	$794.25		$875.8309	$875.82	$875.85	$875.90