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	$162.79	3.382%	$168.2956	$168.30	$168.30	$168.30
Purchase #2	$39.43	7.688%	$42.4614	$42.46	$42.45	$42.50
Purchase #3	$156.32	7.761%	$168.452	$168.45	$168.45	$168.50
Purchase #4	$6.46	12.382%	$7.2599	$7.26	$7.25	$7.30
Purchase #5	$150.81	11.653%	$168.3839	$168.38	$168.40	$168.40
Purchase #6	$64.72	6.661%	$69.031	$69.03	$69.05	$69.00
Purchase #7	$165.45	4.735%	$173.2841	$173.28	$173.30	$173.30
7 purchase totals =	$745.98		$797.1679	$797.16	$797.20	$797.30