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	$91.67	8.607%	$99.56	$99.56	$99.55	$99.60
Purchase #2	$144.41	4.756%	$151.2781	$151.28	$151.30	$151.30
Purchase #3	$245.53	8.142%	$265.5211	$265.52	$265.50	$265.50
Purchase #4	$174.46	3.516%	$180.594	$180.59	$180.60	$180.60
Purchase #5	$81.43	7.537%	$87.5674	$87.57	$87.55	$87.60
Purchase #6	$140.50	12.708%	$158.3547	$158.35	$158.35	$158.40
Purchase #7	$100.91	5.179%	$106.1361	$106.14	$106.15	$106.10
7 purchase totals =	$978.91		$1,049.0114	$1,049.01	$1,049.00	$1,049.10