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	$69.87	9.549%	$76.5419	$76.54	$76.55	$76.50
Purchase #2	$129.38	13.191%	$146.4465	$146.45	$146.45	$146.40
Purchase #3	$40.38	8.736%	$43.9076	$43.91	$43.90	$43.90
Purchase #4	$115.52	6.629%	$123.1778	$123.18	$123.20	$123.20
Purchase #5	$84.78	9.622%	$92.9375	$92.94	$92.95	$92.90
Purchase #6	$74.43	11.382%	$82.9016	$82.90	$82.90	$82.90
Purchase #7	$200.91	13.190%	$227.41	$227.41	$227.40	$227.40
7 purchase totals =	$715.27		$793.3229	$793.33	$793.35	$793.20