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	$137.58	3.401%	$142.2591	$142.26	$142.25	$142.30
Purchase #2	$124.92	7.726%	$134.5713	$134.57	$134.55	$134.60
Purchase #3	$156.39	3.797%	$162.3281	$162.33	$162.35	$162.30
Purchase #4	$235.52	4.639%	$246.4458	$246.45	$246.45	$246.40
Purchase #5	$141.55	6.348%	$150.5356	$150.54	$150.55	$150.50
Purchase #6	$138.72	7.787%	$149.5221	$149.52	$149.50	$149.50
Purchase #7	$74.48	10.319%	$82.1656	$82.17	$82.15	$82.20
7 purchase totals =	$1,009.16		$1,067.8276	$1,067.84	$1,067.80	$1,067.80