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	$43.48	5.130%	$45.7105	$45.71	$45.70	$45.70
Purchase #2	$85.61	11.373%	$95.3464	$95.35	$95.35	$95.30
Purchase #3	$160.66	4.396%	$167.7226	$167.72	$167.70	$167.70
Purchase #4	$129.62	10.585%	$143.3403	$143.34	$143.35	$143.30
Purchase #5	$75.96	8.346%	$82.2996	$82.30	$82.30	$82.30
Purchase #6	$24.73	10.859%	$27.4154	$27.42	$27.40	$27.40
Purchase #7	$98.30	6.834%	$105.0178	$105.02	$105.00	$105.00
7 purchase totals =	$618.36		$666.8526	$666.86	$666.80	$666.70