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	$11.40	10.307%	$12.575	$12.58	$12.60	$12.60
Purchase #2	$144.69	12.609%	$162.934	$162.93	$162.95	$162.90
Purchase #3	$158.32	6.542%	$168.6773	$168.68	$168.70	$168.70
Purchase #4	$61.65	11.243%	$68.5813	$68.58	$68.60	$68.60
Purchase #5	$84.40	7.389%	$90.6363	$90.64	$90.65	$90.60
Purchase #6	$150.40	4.683%	$157.4432	$157.44	$157.45	$157.40
Purchase #7	$182.60	7.515%	$196.3224	$196.32	$196.30	$196.30
7 purchase totals =	$793.46		$857.1695	$857.17	$857.25	$857.10