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	$162.98	6.681%	$173.8687	$173.87	$173.85	$173.90
Purchase #2	$109.43	9.115%	$119.4045	$119.40	$119.40	$119.40
Purchase #3	$31.72	11.609%	$35.4024	$35.40	$35.40	$35.40
Purchase #4	$38.86	5.234%	$40.8939	$40.89	$40.90	$40.90
Purchase #5	$24.25	13.144%	$27.4374	$27.44	$27.45	$27.40
Purchase #6	$223.98	3.708%	$232.2852	$232.29	$232.30	$232.30
Purchase #7	$148.67	5.550%	$156.9212	$156.92	$156.90	$156.90
7 purchase totals =	$739.89		$786.2133	$786.21	$786.20	$786.20