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	$242.38	11.364%	$269.9241	$269.92	$269.90	$269.90
Purchase #2	$111.51	12.103%	$125.0061	$125.01	$125.00	$125.00
Purchase #3	$179.97	11.562%	$200.7781	$200.78	$200.80	$200.80
Purchase #4	$145.35	5.873%	$153.8864	$153.89	$153.90	$153.90
Purchase #5	$229.81	12.298%	$258.072	$258.07	$258.05	$258.10
Purchase #6	$39.34	7.655%	$42.3515	$42.35	$42.35	$42.40
Purchase #7	$64.34	13.499%	$73.0253	$73.03	$73.05	$73.00
7 purchase totals =	$1,012.70		$1,123.0435	$1,123.05	$1,123.05	$1,123.10