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	$20.30	10.186%	$22.3678	$22.37	$22.35	$22.40
Purchase #2	$49.41	5.493%	$52.1241	$52.12	$52.10	$52.10
Purchase #3	$19.77	5.853%	$20.9271	$20.93	$20.95	$20.90
Purchase #4	$141.76	3.623%	$146.896	$146.90	$146.90	$146.90
Purchase #5	$176.79	11.181%	$196.5569	$196.56	$196.55	$196.60
Purchase #6	$29.67	7.172%	$31.7979	$31.80	$31.80	$31.80
Purchase #7	$185.81	5.632%	$196.2748	$196.27	$196.25	$196.30
7 purchase totals =	$623.51		$666.9446	$666.95	$666.90	$667.00