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	$135.32	4.838%	$141.8668	$141.87	$141.85	$141.90
Purchase #2	$234.51	12.152%	$263.0077	$263.01	$263.00	$263.00
Purchase #3	$151.86	10.813%	$168.2806	$168.28	$168.30	$168.30
Purchase #4	$127.61	7.125%	$136.7022	$136.70	$136.70	$136.70
Purchase #5	$114.98	5.114%	$120.8601	$120.86	$120.85	$120.90
Purchase #6	$101.85	4.144%	$106.0707	$106.07	$106.05	$106.10
Purchase #7	$92.48	13.285%	$104.766	$104.77	$104.75	$104.80
7 purchase totals =	$958.61		$1,041.5541	$1,041.56	$1,041.50	$1,041.70