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	$158.90	10.138%	$175.0093	$175.01	$175.00	$175.00
Purchase #2	$202.89	9.723%	$222.617	$222.62	$222.60	$222.60
Purchase #3	$153.89	8.834%	$167.4846	$167.48	$167.50	$167.50
Purchase #4	$162.82	3.396%	$168.3494	$168.35	$168.35	$168.30
Purchase #5	$188.45	11.145%	$209.4528	$209.45	$209.45	$209.50
Purchase #6	$55.67	6.629%	$59.3604	$59.36	$59.35	$59.40
Purchase #7	$192.78	12.614%	$217.0973	$217.10	$217.10	$217.10
7 purchase totals =	$1,115.40		$1,219.3708	$1,219.37	$1,219.35	$1,219.40