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	$151.70	11.136%	$168.5933	$168.59	$168.60	$168.60
Purchase #2	$190.86	3.111%	$196.7977	$196.80	$196.80	$196.80
Purchase #3	$46.46	12.350%	$52.1978	$52.20	$52.20	$52.20
Purchase #4	$199.30	9.336%	$217.9066	$217.91	$217.90	$217.90
Purchase #5	$163.40	7.428%	$175.5374	$175.54	$175.55	$175.50
Purchase #6	$67.56	6.395%	$71.8805	$71.88	$71.90	$71.90
Purchase #7	$210.78	9.233%	$230.2413	$230.24	$230.25	$230.20
7 purchase totals =	$1,030.06		$1,113.1546	$1,113.16	$1,113.20	$1,113.10