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	$47.77	10.756%	$52.9081	$52.91	$52.90	$52.90
Purchase #2	$142.56	11.164%	$158.4754	$158.48	$158.50	$158.50
Purchase #3	$245.77	10.188%	$270.809	$270.81	$270.80	$270.80
Purchase #4	$144.31	13.385%	$163.6259	$163.63	$163.65	$163.60
Purchase #5	$174.40	8.503%	$189.2292	$189.23	$189.25	$189.20
Purchase #6	$172.95	9.854%	$189.9925	$189.99	$190.00	$190.00
Purchase #7	$40.56	7.466%	$43.5882	$43.59	$43.60	$43.60
7 purchase totals =	$968.32		$1,068.6283	$1,068.64	$1,068.70	$1,068.60