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	$163.99	4.693%	$171.6861	$171.69	$171.70	$171.70
Purchase #2	$177.90	10.516%	$196.608	$196.61	$196.60	$196.60
Purchase #3	$131.99	6.736%	$140.8808	$140.88	$140.90	$140.90
Purchase #4	$50.98	4.502%	$53.2751	$53.28	$53.30	$53.30
Purchase #5	$14.34	9.465%	$15.6973	$15.70	$15.70	$15.70
Purchase #6	$144.45	9.866%	$158.7014	$158.70	$158.70	$158.70
Purchase #7	$55.63	6.374%	$59.1759	$59.18	$59.20	$59.20
7 purchase totals =	$739.28		$796.0246	$796.04	$796.10	$796.10