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	$222.27	3.519%	$230.0917	$230.09	$230.10	$230.10
Purchase #2	$202.72	3.517%	$209.8497	$209.85	$209.85	$209.80
Purchase #3	$41.40	7.151%	$44.3605	$44.36	$44.35	$44.40
Purchase #4	$7.47	4.723%	$7.8228	$7.82	$7.80	$7.80
Purchase #5	$104.77	4.163%	$109.1316	$109.13	$109.15	$109.10
Purchase #6	$182.85	13.682%	$207.8675	$207.87	$207.85	$207.90
Purchase #7	$89.80	11.245%	$99.898	$99.90	$99.90	$99.90
7 purchase totals =	$851.28		$909.0218	$909.02	$909.00	$909.00