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	$115.92	6.595%	$123.5649	$123.56	$123.55	$123.60
Purchase #2	$40.89	5.530%	$43.1512	$43.15	$43.15	$43.20
Purchase #3	$169.54	5.144%	$178.2611	$178.26	$178.25	$178.30
Purchase #4	$222.83	12.404%	$250.4698	$250.47	$250.45	$250.50
Purchase #5	$213.86	9.683%	$234.5681	$234.57	$234.55	$234.60
Purchase #6	$160.44	4.123%	$167.0549	$167.05	$167.05	$167.10
Purchase #7	$6.39	10.634%	$7.0695	$7.07	$7.05	$7.10
7 purchase totals =	$929.87		$1,004.1395	$1,004.13	$1,004.05	$1,004.40