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	$183.62	11.866%	$205.4083	$205.41	$205.40	$205.40
Purchase #2	$221.36	13.324%	$250.854	$250.85	$250.85	$250.90
Purchase #3	$100.69	12.719%	$113.4968	$113.50	$113.50	$113.50
Purchase #4	$162.62	10.668%	$179.9683	$179.97	$179.95	$180.00
Purchase #5	$82.88	3.175%	$85.5114	$85.51	$85.50	$85.50
Purchase #6	$196.52	11.453%	$219.0274	$219.03	$219.05	$219.00
Purchase #7	$135.84	7.843%	$146.4939	$146.49	$146.50	$146.50
7 purchase totals =	$1,083.53		$1,200.7601	$1,200.76	$1,200.75	$1,200.80