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	$202.71	9.741%	$222.456	$222.46	$222.45	$222.50
Purchase #2	$99.48	7.678%	$107.1181	$107.12	$107.10	$107.10
Purchase #3	$92.62	8.666%	$100.6464	$100.65	$100.65	$100.60
Purchase #4	$91.65	8.281%	$99.2395	$99.24	$99.25	$99.20
Purchase #5	$164.91	11.761%	$184.3051	$184.31	$184.30	$184.30
Purchase #6	$218.51	10.353%	$241.1323	$241.13	$241.15	$241.10
Purchase #7	$69.55	5.814%	$73.5936	$73.59	$73.60	$73.60
7 purchase totals =	$939.43		$1,028.4910	$1,028.50	$1,028.50	$1,028.40