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	$81.71	4.652%	$85.5111	$85.51	$85.50	$85.50
Purchase #2	$86.45	4.553%	$90.3861	$90.39	$90.40	$90.40
Purchase #3	$193.91	8.458%	$210.3109	$210.31	$210.30	$210.30
Purchase #4	$249.59	7.377%	$268.0023	$268.00	$268.00	$268.00
Purchase #5	$38.38	10.240%	$42.3101	$42.31	$42.30	$42.30
Purchase #6	$84.26	3.593%	$87.2875	$87.29	$87.30	$87.30
Purchase #7	$212.39	3.558%	$219.9468	$219.95	$219.95	$219.90
7 purchase totals =	$946.69		$1,003.7548	$1,003.76	$1,003.75	$1,003.70