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	$41.71	8.778%	$45.3713	$45.37	$45.35	$45.40
Purchase #2	$136.75	3.335%	$141.3106	$141.31	$141.30	$141.30
Purchase #3	$45.83	8.253%	$49.6123	$49.61	$49.60	$49.60
Purchase #4	$75.26	5.586%	$79.464	$79.46	$79.45	$79.50
Purchase #5	$185.46	13.711%	$210.8884	$210.89	$210.90	$210.90
Purchase #6	$49.83	6.380%	$53.0092	$53.01	$53.00	$53.00
Purchase #7	$92.73	11.635%	$103.5191	$103.52	$103.50	$103.50
7 purchase totals =	$627.57		$683.1749	$683.17	$683.10	$683.20