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	$240.59	10.147%	$265.0027	$265.00	$265.00	$265.00
Purchase #2	$197.89	11.835%	$221.3103	$221.31	$221.30	$221.30
Purchase #3	$123.45	8.359%	$133.7692	$133.77	$133.75	$133.80
Purchase #4	$187.93	13.462%	$213.2291	$213.23	$213.25	$213.20
Purchase #5	$10.45	4.657%	$10.9367	$10.94	$10.95	$10.90
Purchase #6	$190.25	12.771%	$214.5468	$214.55	$214.55	$214.50
Purchase #7	$110.81	11.401%	$123.4434	$123.44	$123.45	$123.40
7 purchase totals =	$1,061.37		$1,182.2382	$1,182.24	$1,182.25	$1,182.10