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	$41.89	3.788%	$43.4768	$43.48	$43.50	$43.50
Purchase #2	$219.56	11.860%	$245.5998	$245.60	$245.60	$245.60
Purchase #3	$83.92	7.654%	$90.3432	$90.34	$90.35	$90.30
Purchase #4	$154.51	11.659%	$172.5243	$172.52	$172.50	$172.50
Purchase #5	$180.29	8.335%	$195.3172	$195.32	$195.30	$195.30
Purchase #6	$62.71	7.431%	$67.37	$67.37	$67.35	$67.40
Purchase #7	$67.44	5.725%	$71.3009	$71.30	$71.30	$71.30
7 purchase totals =	$810.32		$885.9322	$885.93	$885.90	$885.90