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	$213.41	10.776%	$236.4071	$236.41	$236.40	$236.40
Purchase #2	$58.53	13.677%	$66.5351	$66.54	$66.55	$66.50
Purchase #3	$115.43	6.751%	$123.2227	$123.22	$123.20	$123.20
Purchase #4	$50.64	3.146%	$52.2331	$52.23	$52.25	$52.20
Purchase #5	$54.80	11.485%	$61.0938	$61.09	$61.10	$61.10
Purchase #6	$233.29	13.814%	$265.5167	$265.52	$265.50	$265.50
Purchase #7	$200.33	7.828%	$216.0118	$216.01	$216.00	$216.00
7 purchase totals =	$926.43		$1,021.0203	$1,021.02	$1,021.00	$1,020.90