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	$73.53	4.563%	$76.8852	$76.89	$76.90	$76.90
Purchase #2	$83.93	9.138%	$91.5995	$91.60	$91.60	$91.60
Purchase #3	$239.54	12.788%	$270.1724	$270.17	$270.15	$270.20
Purchase #4	$39.66	10.543%	$43.8414	$43.84	$43.85	$43.80
Purchase #5	$83.47	7.610%	$89.8221	$89.82	$89.80	$89.80
Purchase #6	$191.93	13.558%	$217.9519	$217.95	$217.95	$218.00
Purchase #7	$100.89	5.498%	$106.4369	$106.44	$106.45	$106.40
7 purchase totals =	$812.95		$896.7094	$896.71	$896.70	$896.70