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	$76.45	11.740%	$85.4252	$85.43	$85.45	$85.40
Purchase #2	$187.83	10.816%	$208.1457	$208.15	$208.15	$208.10
Purchase #3	$66.44	7.372%	$71.338	$71.34	$71.35	$71.30
Purchase #4	$233.68	3.714%	$242.3589	$242.36	$242.35	$242.40
Purchase #5	$135.31	5.330%	$142.522	$142.52	$142.50	$142.50
Purchase #6	$54.61	10.794%	$60.5046	$60.50	$60.50	$60.50
Purchase #7	$95.65	4.773%	$100.2154	$100.22	$100.20	$100.20
7 purchase totals =	$849.97		$910.5098	$910.52	$910.50	$910.40