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	$211.46	7.438%	$227.1884	$227.19	$227.20	$227.20
Purchase #2	$82.28	4.317%	$85.832	$85.83	$85.85	$85.80
Purchase #3	$79.32	12.685%	$89.3817	$89.38	$89.40	$89.40
Purchase #4	$145.79	11.684%	$162.8241	$162.82	$162.80	$162.80
Purchase #5	$250.30	13.173%	$283.272	$283.27	$283.25	$283.30
Purchase #6	$37.73	4.137%	$39.2909	$39.29	$39.30	$39.30
Purchase #7	$61.90	9.208%	$67.5998	$67.60	$67.60	$67.60
7 purchase totals =	$868.78		$955.3889	$955.38	$955.40	$955.40