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	$147.54	6.292%	$156.8232	$156.82	$156.80	$156.80
Purchase #2	$208.27	8.483%	$225.9375	$225.94	$225.95	$225.90
Purchase #3	$144.25	4.869%	$151.2735	$151.27	$151.25	$151.30
Purchase #4	$105.69	12.617%	$119.0249	$119.02	$119.00	$119.00
Purchase #5	$114.26	11.771%	$127.7095	$127.71	$127.70	$127.70
Purchase #6	$209.47	3.802%	$217.434	$217.43	$217.45	$217.40
Purchase #7	$141.61	7.465%	$152.1812	$152.18	$152.20	$152.20
7 purchase totals =	$1,071.09		$1,150.3838	$1,150.37	$1,150.35	$1,150.30