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	$98.47	12.670%	$110.9461	$110.95	$110.95	$110.90
Purchase #2	$162.83	11.151%	$180.9872	$180.99	$181.00	$181.00
Purchase #3	$159.48	10.478%	$176.1903	$176.19	$176.20	$176.20
Purchase #4	$117.82	4.820%	$123.4989	$123.50	$123.50	$123.50
Purchase #5	$120.75	5.654%	$127.5772	$127.58	$127.60	$127.60
Purchase #6	$143.60	11.773%	$160.506	$160.51	$160.50	$160.50
Purchase #7	$59.87	3.457%	$61.9397	$61.94	$61.95	$61.90
7 purchase totals =	$862.82		$941.6454	$941.66	$941.70	$941.60