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	$136.89	12.829%	$154.4516	$154.45	$154.45	$154.50
Purchase #2	$69.41	5.811%	$73.4434	$73.44	$73.45	$73.40
Purchase #3	$72.67	11.103%	$80.7386	$80.74	$80.75	$80.70
Purchase #4	$248.76	5.202%	$261.7005	$261.70	$261.70	$261.70
Purchase #5	$167.40	7.673%	$180.2446	$180.24	$180.25	$180.20
Purchase #6	$240.32	13.667%	$273.1645	$273.16	$273.15	$273.20
Purchase #7	$83.96	6.734%	$89.6139	$89.61	$89.60	$89.60
7 purchase totals =	$1,019.41		$1,113.3571	$1,113.34	$1,113.35	$1,113.30