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	$71.64	8.118%	$77.4557	$77.46	$77.45	$77.50
Purchase #2	$50.77	13.111%	$57.4265	$57.43	$57.45	$57.40
Purchase #3	$138.98	12.197%	$155.9314	$155.93	$155.95	$155.90
Purchase #4	$181.98	5.272%	$191.574	$191.57	$191.55	$191.60
Purchase #5	$6.66	12.117%	$7.467	$7.47	$7.45	$7.50
Purchase #6	$243.25	13.784%	$276.7796	$276.78	$276.80	$276.80
Purchase #7	$85.59	3.511%	$88.5951	$88.60	$88.60	$88.60
7 purchase totals =	$778.87		$855.2293	$855.24	$855.25	$855.30