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	$213.33	10.619%	$235.9835	$235.98	$236.00	$236.00
Purchase #2	$31.26	4.140%	$32.5542	$32.55	$32.55	$32.60
Purchase #3	$133.56	4.440%	$139.4901	$139.49	$139.50	$139.50
Purchase #4	$61.43	6.658%	$65.52	$65.52	$65.50	$65.50
Purchase #5	$60.44	10.647%	$66.875	$66.88	$66.90	$66.90
Purchase #6	$76.71	7.576%	$82.5215	$82.52	$82.50	$82.50
Purchase #7	$38.47	5.440%	$40.5628	$40.56	$40.55	$40.60
7 purchase totals =	$615.20		$663.5071	$663.50	$663.50	$663.60