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	$107.28	6.207%	$113.9389	$113.94	$113.95	$113.90
Purchase #2	$51.94	13.771%	$59.0927	$59.09	$59.10	$59.10
Purchase #3	$209.74	11.795%	$234.4788	$234.48	$234.50	$234.50
Purchase #4	$156.32	3.812%	$162.2789	$162.28	$162.30	$162.30
Purchase #5	$198.65	4.149%	$206.892	$206.89	$206.90	$206.90
Purchase #6	$72.88	4.794%	$76.3739	$76.37	$76.35	$76.40
Purchase #7	$51.74	3.311%	$53.4531	$53.45	$53.45	$53.50
7 purchase totals =	$848.55		$906.5083	$906.50	$906.55	$906.60