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	$146.33	8.547%	$158.8368	$158.84	$158.85	$158.80
Purchase #2	$124.89	11.410%	$139.1399	$139.14	$139.15	$139.10
Purchase #3	$15.54	5.725%	$16.4297	$16.43	$16.45	$16.40
Purchase #4	$146.95	10.760%	$162.7618	$162.76	$162.75	$162.80
Purchase #5	$89.58	3.720%	$92.9124	$92.91	$92.90	$92.90
Purchase #6	$188.62	6.503%	$200.886	$200.89	$200.90	$200.90
Purchase #7	$245.95	9.121%	$268.3831	$268.38	$268.40	$268.40
7 purchase totals =	$957.86		$1,039.3497	$1,039.35	$1,039.40	$1,039.30