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	$72.95	13.771%	$82.9959	$83.00	$83.00	$83.00
Purchase #2	$42.89	3.123%	$44.2295	$44.23	$44.25	$44.20
Purchase #3	$136.25	13.851%	$155.122	$155.12	$155.10	$155.10
Purchase #4	$134.50	5.145%	$141.42	$141.42	$141.40	$141.40
Purchase #5	$40.36	12.738%	$45.5011	$45.50	$45.50	$45.50
Purchase #6	$103.63	10.772%	$114.793	$114.79	$114.80	$114.80
Purchase #7	$146.55	10.487%	$161.9187	$161.92	$161.90	$161.90
7 purchase totals =	$677.13		$745.9802	$745.98	$745.95	$745.90