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	$219.61	3.770%	$227.8893	$227.89	$227.90	$227.90
Purchase #2	$51.33	4.152%	$53.4612	$53.46	$53.45	$53.50
Purchase #3	$125.89	4.531%	$131.5941	$131.59	$131.60	$131.60
Purchase #4	$57.87	11.401%	$64.4678	$64.47	$64.45	$64.50
Purchase #5	$198.37	5.370%	$209.0225	$209.02	$209.00	$209.00
Purchase #6	$58.60	6.870%	$62.6258	$62.63	$62.65	$62.60
Purchase #7	$192.30	7.544%	$206.8071	$206.81	$206.80	$206.80
7 purchase totals =	$903.97		$955.8678	$955.87	$955.85	$955.90