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	$80.31	7.593%	$86.4079	$86.41	$86.40	$86.40
Purchase #2	$88.36	11.859%	$98.8386	$98.84	$98.85	$98.80
Purchase #3	$198.48	12.226%	$222.7462	$222.75	$222.75	$222.70
Purchase #4	$24.47	8.726%	$26.6053	$26.61	$26.60	$26.60
Purchase #5	$14.54	4.256%	$15.1588	$15.16	$15.15	$15.20
Purchase #6	$55.28	13.215%	$62.5853	$62.59	$62.60	$62.60
Purchase #7	$52.34	3.805%	$54.3315	$54.33	$54.35	$54.30
7 purchase totals =	$513.78		$566.6736	$566.69	$566.70	$566.60