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	$133.43	6.605%	$142.2431	$142.24	$142.25	$142.20
Purchase #2	$95.48	4.195%	$99.4854	$99.49	$99.50	$99.50
Purchase #3	$38.90	9.549%	$42.6146	$42.61	$42.60	$42.60
Purchase #4	$243.45	4.853%	$255.2646	$255.26	$255.25	$255.30
Purchase #5	$211.56	11.839%	$236.6066	$236.61	$236.60	$236.60
Purchase #6	$77.36	3.801%	$80.3005	$80.30	$80.30	$80.30
Purchase #7	$75.73	11.724%	$84.6086	$84.61	$84.60	$84.60
7 purchase totals =	$875.91		$941.1234	$941.12	$941.10	$941.10