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	$133.95	9.102%	$146.1421	$146.14	$146.15	$146.10
Purchase #2	$144.97	10.682%	$160.4557	$160.46	$160.45	$160.50
Purchase #3	$5.29	9.808%	$5.8088	$5.81	$5.80	$5.80
Purchase #4	$19.97	5.633%	$21.0949	$21.09	$21.10	$21.10
Purchase #5	$103.68	5.238%	$109.1108	$109.11	$109.10	$109.10
Purchase #6	$80.33	11.804%	$89.8122	$89.81	$89.80	$89.80
Purchase #7	$172.54	12.735%	$194.513	$194.51	$194.50	$194.50
7 purchase totals =	$660.73		$726.9375	$726.93	$726.90	$726.90