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	$38.47	13.361%	$43.61	$43.61	$43.60	$43.60
Purchase #2	$210.33	5.601%	$222.1106	$222.11	$222.10	$222.10
Purchase #3	$52.59	12.530%	$59.1795	$59.18	$59.20	$59.20
Purchase #4	$75.85	6.840%	$81.0381	$81.04	$81.05	$81.00
Purchase #5	$144.63	13.849%	$164.6598	$164.66	$164.65	$164.70
Purchase #6	$201.89	13.557%	$229.2602	$229.26	$229.25	$229.30
Purchase #7	$75.46	8.253%	$81.6877	$81.69	$81.70	$81.70
7 purchase totals =	$799.22		$881.5459	$881.55	$881.55	$881.60