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	$237.27	13.557%	$269.4367	$269.44	$269.45	$269.40
Purchase #2	$79.57	12.803%	$89.7573	$89.76	$89.75	$89.80
Purchase #3	$114.55	5.178%	$120.4814	$120.48	$120.50	$120.50
Purchase #4	$248.94	7.114%	$266.6496	$266.65	$266.65	$266.60
Purchase #5	$129.80	12.700%	$146.2846	$146.28	$146.30	$146.30
Purchase #6	$192.29	13.849%	$218.9202	$218.92	$218.90	$218.90
Purchase #7	$140.25	8.123%	$151.6425	$151.64	$151.65	$151.60
7 purchase totals =	$1,142.67		$1,263.1723	$1,263.17	$1,263.20	$1,263.10