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	$226.94	3.103%	$233.9819	$233.98	$234.00	$234.00
Purchase #2	$104.28	9.705%	$114.4004	$114.40	$114.40	$114.40
Purchase #3	$10.29	3.341%	$10.6338	$10.63	$10.65	$10.60
Purchase #4	$10.91	11.131%	$12.1244	$12.12	$12.10	$12.10
Purchase #5	$40.88	6.752%	$43.6402	$43.64	$43.65	$43.60
Purchase #6	$53.89	11.114%	$59.8793	$59.88	$59.90	$59.90
Purchase #7	$233.62	13.263%	$264.605	$264.61	$264.60	$264.60
7 purchase totals =	$680.81		$739.2650	$739.26	$739.30	$739.20