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	$76.69	10.841%	$85.004	$85.00	$85.00	$85.00
Purchase #2	$48.69	11.159%	$54.1233	$54.12	$54.10	$54.10
Purchase #3	$36.83	8.287%	$39.8821	$39.88	$39.90	$39.90
Purchase #4	$243.63	12.387%	$273.8084	$273.81	$273.80	$273.80
Purchase #5	$239.29	12.672%	$269.6128	$269.61	$269.60	$269.60
Purchase #6	$54.39	13.790%	$61.8904	$61.89	$61.90	$61.90
Purchase #7	$178.48	11.867%	$199.6602	$199.66	$199.65	$199.70
7 purchase totals =	$878.00		$983.9812	$983.97	$983.95	$984.00