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	$218.82	9.162%	$238.8683	$238.87	$238.85	$238.90
Purchase #2	$130.77	7.280%	$140.2901	$140.29	$140.30	$140.30
Purchase #3	$139.92	10.399%	$154.4703	$154.47	$154.45	$154.50
Purchase #4	$237.68	3.504%	$246.0083	$246.01	$246.00	$246.00
Purchase #5	$185.58	13.415%	$210.4756	$210.48	$210.50	$210.50
Purchase #6	$134.81	10.415%	$148.8505	$148.85	$148.85	$148.90
Purchase #7	$65.37	11.586%	$72.9438	$72.94	$72.95	$72.90
7 purchase totals =	$1,112.95		$1,211.9069	$1,211.91	$1,211.90	$1,212.00