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	$55.77	9.636%	$61.144	$61.14	$61.15	$61.10
Purchase #2	$52.83	13.715%	$60.0756	$60.08	$60.10	$60.10
Purchase #3	$147.43	13.123%	$166.7772	$166.78	$166.80	$166.80
Purchase #4	$185.29	12.667%	$208.7607	$208.76	$208.75	$208.80
Purchase #5	$210.64	4.606%	$220.3421	$220.34	$220.35	$220.30
Purchase #6	$72.94	7.700%	$78.5564	$78.56	$78.55	$78.60
Purchase #7	$44.35	5.615%	$46.8403	$46.84	$46.85	$46.80
7 purchase totals =	$769.25		$842.4963	$842.50	$842.55	$842.50