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	$72.86	4.794%	$76.3529	$76.35	$76.35	$76.40
Purchase #2	$91.49	9.401%	$100.091	$100.09	$100.10	$100.10
Purchase #3	$47.30	7.538%	$50.8655	$50.87	$50.85	$50.90
Purchase #4	$72.72	6.756%	$77.633	$77.63	$77.65	$77.60
Purchase #5	$183.47	3.314%	$189.5502	$189.55	$189.55	$189.60
Purchase #6	$244.37	10.675%	$270.4565	$270.46	$270.45	$270.50
Purchase #7	$67.55	6.322%	$71.8205	$71.82	$71.80	$71.80
7 purchase totals =	$779.76		$836.7696	$836.77	$836.75	$836.90