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	$185.65	13.120%	$210.0073	$210.01	$210.00	$210.00
Purchase #2	$169.47	13.657%	$192.6145	$192.61	$192.60	$192.60
Purchase #3	$168.39	8.533%	$182.7587	$182.76	$182.75	$182.80
Purchase #4	$28.45	12.788%	$32.0882	$32.09	$32.10	$32.10
Purchase #5	$150.30	5.479%	$158.5349	$158.53	$158.55	$158.50
Purchase #6	$43.36	9.754%	$47.5893	$47.59	$47.60	$47.60
Purchase #7	$215.63	11.714%	$240.8889	$240.89	$240.90	$240.90
7 purchase totals =	$961.25		$1,064.4818	$1,064.48	$1,064.50	$1,064.50