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	$47.79	13.506%	$54.2445	$54.24	$54.25	$54.20
Purchase #2	$88.79	12.696%	$100.0628	$100.06	$100.05	$100.10
Purchase #3	$230.59	5.721%	$243.7821	$243.78	$243.80	$243.80
Purchase #4	$18.48	10.650%	$20.4481	$20.45	$20.45	$20.40
Purchase #5	$181.89	5.167%	$191.2883	$191.29	$191.30	$191.30
Purchase #6	$241.53	4.547%	$252.5124	$252.51	$252.50	$252.50
Purchase #7	$200.57	7.610%	$215.8334	$215.83	$215.85	$215.80
7 purchase totals =	$1,009.64		$1,078.1716	$1,078.16	$1,078.20	$1,078.10