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	$64.94	3.847%	$67.4382	$67.44	$67.45	$67.40
Purchase #2	$132.36	5.309%	$139.387	$139.39	$139.40	$139.40
Purchase #3	$10.87	11.283%	$12.0965	$12.10	$12.10	$12.10
Purchase #4	$92.79	13.443%	$105.2638	$105.26	$105.25	$105.30
Purchase #5	$60.68	4.454%	$63.3827	$63.38	$63.40	$63.40
Purchase #6	$31.69	13.240%	$35.8858	$35.89	$35.90	$35.90
Purchase #7	$197.28	13.760%	$224.4257	$224.43	$224.45	$224.40
7 purchase totals =	$590.61		$647.8797	$647.89	$647.95	$647.90