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	$163.48	11.347%	$182.0301	$182.03	$182.05	$182.00
Purchase #2	$40.60	11.104%	$45.1082	$45.11	$45.10	$45.10
Purchase #3	$40.54	6.116%	$43.0194	$43.02	$43.00	$43.00
Purchase #4	$20.26	4.848%	$21.2422	$21.24	$21.25	$21.20
Purchase #5	$55.47	12.719%	$62.5252	$62.53	$62.55	$62.50
Purchase #6	$32.43	7.386%	$34.8253	$34.83	$34.85	$34.80
Purchase #7	$55.62	11.651%	$62.1003	$62.10	$62.10	$62.10
7 purchase totals =	$408.40		$450.8507	$450.86	$450.90	$450.70