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	$116.84	12.329%	$131.2452	$131.25	$131.25	$131.20
Purchase #2	$144.68	4.283%	$150.8766	$150.88	$150.90	$150.90
Purchase #3	$215.61	12.360%	$242.2594	$242.26	$242.25	$242.30
Purchase #4	$9.62	5.397%	$10.1392	$10.14	$10.15	$10.10
Purchase #5	$99.34	13.781%	$113.03	$113.03	$113.05	$113.00
Purchase #6	$207.26	10.421%	$228.8586	$228.86	$228.85	$228.90
Purchase #7	$182.72	4.785%	$191.4632	$191.46	$191.45	$191.50
7 purchase totals =	$976.07		$1,067.8722	$1,067.88	$1,067.90	$1,067.90