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	$31.31	13.319%	$35.4802	$35.48	$35.50	$35.50
Purchase #2	$148.98	6.307%	$158.3762	$158.38	$158.40	$158.40
Purchase #3	$151.70	5.872%	$160.6078	$160.61	$160.60	$160.60
Purchase #4	$183.35	3.644%	$190.0313	$190.03	$190.05	$190.00
Purchase #5	$13.96	4.142%	$14.5382	$14.54	$14.55	$14.50
Purchase #6	$23.34	7.215%	$25.024	$25.02	$25.00	$25.00
Purchase #7	$108.32	4.823%	$113.5443	$113.54	$113.55	$113.50
7 purchase totals =	$660.96		$697.6020	$697.60	$697.65	$697.50