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	$49.88	3.228%	$51.4901	$51.49	$51.50	$51.50
Purchase #2	$70.73	10.381%	$78.0725	$78.07	$78.05	$78.10
Purchase #3	$108.43	7.190%	$116.2261	$116.23	$116.25	$116.20
Purchase #4	$229.63	8.831%	$249.9086	$249.91	$249.90	$249.90
Purchase #5	$175.90	11.158%	$195.5269	$195.53	$195.55	$195.50
Purchase #6	$221.32	9.469%	$242.2768	$242.28	$242.30	$242.30
Purchase #7	$29.66	9.789%	$32.5634	$32.56	$32.55	$32.60
7 purchase totals =	$885.55		$966.0644	$966.07	$966.10	$966.10