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	$49.39	12.186%	$55.4087	$55.41	$55.40	$55.40
Purchase #2	$11.33	11.329%	$12.6136	$12.61	$12.60	$12.60
Purchase #3	$244.67	7.593%	$263.2478	$263.25	$263.25	$263.20
Purchase #4	$224.64	7.233%	$240.8882	$240.89	$240.90	$240.90
Purchase #5	$143.31	6.844%	$153.1181	$153.12	$153.10	$153.10
Purchase #6	$145.77	5.216%	$153.3734	$153.37	$153.35	$153.40
Purchase #7	$233.91	11.705%	$261.2892	$261.29	$261.30	$261.30
7 purchase totals =	$1,053.02		$1,139.9390	$1,139.94	$1,139.90	$1,139.90