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	$172.98	13.784%	$196.8236	$196.82	$196.80	$196.80
Purchase #2	$238.51	5.808%	$252.3627	$252.36	$252.35	$252.40
Purchase #3	$199.92	9.614%	$219.1403	$219.14	$219.15	$219.10
Purchase #4	$210.91	11.364%	$234.8778	$234.88	$234.90	$234.90
Purchase #5	$57.98	3.104%	$59.7797	$59.78	$59.80	$59.80
Purchase #6	$103.49	10.400%	$114.253	$114.25	$114.25	$114.30
Purchase #7	$181.49	9.226%	$198.2343	$198.23	$198.25	$198.20
7 purchase totals =	$1,165.28		$1,275.4714	$1,275.46	$1,275.50	$1,275.50