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	$126.47	13.194%	$143.1565	$143.16	$143.15	$143.20
Purchase #2	$25.70	11.331%	$28.6121	$28.61	$28.60	$28.60
Purchase #3	$78.50	3.109%	$80.9406	$80.94	$80.95	$80.90
Purchase #4	$226.98	11.714%	$253.5684	$253.57	$253.55	$253.60
Purchase #5	$137.50	10.794%	$152.3418	$152.34	$152.35	$152.30
Purchase #6	$116.93	6.392%	$124.4042	$124.40	$124.40	$124.40
Purchase #7	$213.90	9.442%	$234.0964	$234.10	$234.10	$234.10
7 purchase totals =	$925.98		$1,017.1200	$1,017.12	$1,017.10	$1,017.10