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	$44.88	8.550%	$48.7172	$48.72	$48.70	$48.70
Purchase #2	$80.44	3.546%	$83.2924	$83.29	$83.30	$83.30
Purchase #3	$216.31	13.485%	$245.4794	$245.48	$245.50	$245.50
Purchase #4	$208.96	5.207%	$219.8405	$219.84	$219.85	$219.80
Purchase #5	$234.57	3.322%	$242.3624	$242.36	$242.35	$242.40
Purchase #6	$54.72	13.177%	$61.9305	$61.93	$61.95	$61.90
Purchase #7	$123.95	5.692%	$131.0052	$131.01	$131.00	$131.00
7 purchase totals =	$963.83		$1,032.6276	$1,032.63	$1,032.65	$1,032.60