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	$60.62	10.448%	$66.9536	$66.95	$66.95	$67.00
Purchase #2	$141.54	4.489%	$147.8937	$147.89	$147.90	$147.90
Purchase #3	$79.82	8.387%	$86.5145	$86.51	$86.50	$86.50
Purchase #4	$31.31	3.669%	$32.4588	$32.46	$32.45	$32.50
Purchase #5	$57.94	11.739%	$64.7416	$64.74	$64.75	$64.70
Purchase #6	$166.40	7.765%	$179.321	$179.32	$179.30	$179.30
Purchase #7	$92.66	10.360%	$102.2596	$102.26	$102.25	$102.30
7 purchase totals =	$630.29		$680.1428	$680.13	$680.10	$680.20