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	$98.82	6.203%	$104.9498	$104.95	$104.95	$104.90
Purchase #2	$206.51	13.120%	$233.6041	$233.60	$233.60	$233.60
Purchase #3	$54.51	9.859%	$59.8841	$59.88	$59.90	$59.90
Purchase #4	$205.42	11.675%	$229.4028	$229.40	$229.40	$229.40
Purchase #5	$43.68	3.527%	$45.2206	$45.22	$45.20	$45.20
Purchase #6	$38.63	8.484%	$41.9074	$41.91	$41.90	$41.90
Purchase #7	$48.90	8.615%	$53.1127	$53.11	$53.10	$53.10
7 purchase totals =	$696.47		$768.0815	$768.07	$768.05	$768.00