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	$98.59	7.144%	$105.6333	$105.63	$105.65	$105.60
Purchase #2	$167.32	13.607%	$190.0872	$190.09	$190.10	$190.10
Purchase #3	$158.86	10.516%	$175.5657	$175.57	$175.55	$175.60
Purchase #4	$153.41	4.665%	$160.5666	$160.57	$160.55	$160.60
Purchase #5	$35.49	4.285%	$37.0107	$37.01	$37.00	$37.00
Purchase #6	$12.70	9.279%	$13.8784	$13.88	$13.90	$13.90
Purchase #7	$81.41	7.291%	$87.3456	$87.35	$87.35	$87.30
7 purchase totals =	$707.78		$770.0875	$770.10	$770.10	$770.10