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	$94.72	5.186%	$99.6322	$99.63	$99.65	$99.60
Purchase #2	$116.70	5.482%	$123.0975	$123.10	$123.10	$123.10
Purchase #3	$147.42	10.357%	$162.6883	$162.69	$162.70	$162.70
Purchase #4	$215.74	13.873%	$245.6696	$245.67	$245.65	$245.70
Purchase #5	$132.57	6.867%	$141.6736	$141.67	$141.65	$141.70
Purchase #6	$119.36	5.614%	$126.0609	$126.06	$126.05	$126.10
Purchase #7	$208.81	9.710%	$229.0855	$229.09	$229.10	$229.10
7 purchase totals =	$1,035.32		$1,127.9076	$1,127.91	$1,127.90	$1,128.00