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	$149.81	5.366%	$157.8488	$157.85	$157.85	$157.80
Purchase #2	$127.38	6.641%	$135.8393	$135.84	$135.85	$135.80
Purchase #3	$238.75	7.166%	$255.8588	$255.86	$255.85	$255.90
Purchase #4	$176.61	4.362%	$184.3137	$184.31	$184.30	$184.30
Purchase #5	$125.81	9.278%	$137.4827	$137.48	$137.50	$137.50
Purchase #6	$135.59	10.633%	$150.0073	$150.01	$150.00	$150.00
Purchase #7	$6.86	9.314%	$7.4989	$7.50	$7.50	$7.50
7 purchase totals =	$960.81		$1,028.8495	$1,028.85	$1,028.85	$1,028.80