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	$67.55	6.623%	$72.0238	$72.02	$72.00	$72.00
Purchase #2	$220.91	6.442%	$235.141	$235.14	$235.15	$235.10
Purchase #3	$87.31	3.466%	$90.3362	$90.34	$90.35	$90.30
Purchase #4	$144.99	13.246%	$164.1954	$164.20	$164.20	$164.20
Purchase #5	$237.32	12.405%	$266.7595	$266.76	$266.75	$266.80
Purchase #6	$131.78	3.871%	$136.8812	$136.88	$136.90	$136.90
Purchase #7	$160.38	3.610%	$166.1697	$166.17	$166.15	$166.20
7 purchase totals =	$1,050.24		$1,131.5068	$1,131.51	$1,131.50	$1,131.50