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	$22.81	9.166%	$24.9008	$24.90	$24.90	$24.90
Purchase #2	$59.67	12.698%	$67.2469	$67.25	$67.25	$67.20
Purchase #3	$56.32	9.632%	$61.7447	$61.74	$61.75	$61.70
Purchase #4	$174.62	6.856%	$186.5919	$186.59	$186.60	$186.60
Purchase #5	$101.55	4.695%	$106.3178	$106.32	$106.30	$106.30
Purchase #6	$78.57	5.374%	$82.7924	$82.79	$82.80	$82.80
Purchase #7	$112.25	10.125%	$123.6153	$123.62	$123.60	$123.60
7 purchase totals =	$605.79		$653.2098	$653.21	$653.20	$653.10