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	$190.25	6.610%	$202.8255	$202.83	$202.85	$202.80
Purchase #2	$164.35	11.278%	$182.8854	$182.89	$182.90	$182.90
Purchase #3	$123.57	9.347%	$135.1201	$135.12	$135.10	$135.10
Purchase #4	$99.52	7.399%	$106.8835	$106.88	$106.90	$106.90
Purchase #5	$39.36	13.262%	$44.5799	$44.58	$44.60	$44.60
Purchase #6	$165.46	4.261%	$172.5103	$172.51	$172.50	$172.50
Purchase #7	$41.32	3.412%	$42.7298	$42.73	$42.75	$42.70
7 purchase totals =	$823.83		$887.5345	$887.54	$887.60	$887.50