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	$113.41	11.287%	$126.2106	$126.21	$126.20	$126.20
Purchase #2	$248.26	13.405%	$281.5393	$281.54	$281.55	$281.50
Purchase #3	$200.71	4.277%	$209.2944	$209.29	$209.30	$209.30
Purchase #4	$72.55	13.661%	$82.4611	$82.46	$82.45	$82.50
Purchase #5	$159.71	11.573%	$178.1932	$178.19	$178.20	$178.20
Purchase #6	$27.45	3.769%	$28.4846	$28.48	$28.50	$28.50
Purchase #7	$159.98	10.145%	$176.21	$176.21	$176.20	$176.20
7 purchase totals =	$982.07		$1,082.3932	$1,082.38	$1,082.40	$1,082.40