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	$142.74	13.530%	$162.0527	$162.05	$162.05	$162.10
Purchase #2	$219.79	3.607%	$227.7178	$227.72	$227.70	$227.70
Purchase #3	$111.90	11.127%	$124.3511	$124.35	$124.35	$124.40
Purchase #4	$76.53	3.772%	$79.4167	$79.42	$79.40	$79.40
Purchase #5	$78.42	8.407%	$85.0128	$85.01	$85.00	$85.00
Purchase #6	$163.53	10.603%	$180.8691	$180.87	$180.85	$180.90
Purchase #7	$138.68	3.408%	$143.4062	$143.41	$143.40	$143.40
7 purchase totals =	$931.59		$1,002.8264	$1,002.83	$1,002.75	$1,002.90