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	$68.86	3.285%	$71.1221	$71.12	$71.10	$71.10
Purchase #2	$31.50	4.222%	$32.8299	$32.83	$32.85	$32.80
Purchase #3	$44.66	6.224%	$47.4396	$47.44	$47.45	$47.40
Purchase #4	$84.33	6.242%	$89.5939	$89.59	$89.60	$89.60
Purchase #5	$11.62	9.584%	$12.7337	$12.73	$12.75	$12.70
Purchase #6	$178.88	11.802%	$199.9914	$199.99	$200.00	$200.00
Purchase #7	$172.37	13.634%	$195.8709	$195.87	$195.85	$195.90
7 purchase totals =	$592.22		$649.5815	$649.57	$649.60	$649.50