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	$145.89	6.835%	$155.8616	$155.86	$155.85	$155.90
Purchase #2	$155.34	4.778%	$162.7621	$162.76	$162.75	$162.80
Purchase #3	$153.57	10.634%	$169.9006	$169.90	$169.90	$169.90
Purchase #4	$196.68	13.133%	$222.51	$222.51	$222.50	$222.50
Purchase #5	$226.28	12.357%	$254.2414	$254.24	$254.25	$254.20
Purchase #6	$215.30	7.663%	$231.7984	$231.80	$231.80	$231.80
Purchase #7	$236.69	5.766%	$250.3375	$250.34	$250.35	$250.30
7 purchase totals =	$1,329.75		$1,447.4116	$1,447.41	$1,447.40	$1,447.40