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	$98.84	13.857%	$112.5363	$112.54	$112.55	$112.50
Purchase #2	$211.62	8.440%	$229.4807	$229.48	$229.50	$229.50
Purchase #3	$217.74	5.629%	$229.9966	$230.00	$230.00	$230.00
Purchase #4	$21.43	12.734%	$24.1589	$24.16	$24.15	$24.20
Purchase #5	$215.66	11.363%	$240.1654	$240.17	$240.15	$240.20
Purchase #6	$172.41	7.835%	$185.9183	$185.92	$185.90	$185.90
Purchase #7	$75.77	3.502%	$78.4235	$78.42	$78.40	$78.40
7 purchase totals =	$1,013.47		$1,100.6797	$1,100.69	$1,100.65	$1,100.70