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	$37.98	10.266%	$41.879	$41.88	$41.90	$41.90
Purchase #2	$59.86	11.270%	$66.6062	$66.61	$66.60	$66.60
Purchase #3	$207.68	7.485%	$223.2248	$223.22	$223.20	$223.20
Purchase #4	$164.77	4.297%	$171.8502	$171.85	$171.85	$171.90
Purchase #5	$106.40	4.491%	$111.1784	$111.18	$111.20	$111.20
Purchase #6	$238.37	6.692%	$254.3217	$254.32	$254.30	$254.30
Purchase #7	$123.29	10.394%	$136.1048	$136.10	$136.10	$136.10
7 purchase totals =	$938.35		$1,005.1651	$1,005.16	$1,005.15	$1,005.20