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	$222.26	10.359%	$245.2839	$245.28	$245.30	$245.30
Purchase #2	$59.30	12.253%	$66.566	$66.57	$66.55	$66.60
Purchase #3	$106.39	10.460%	$117.5184	$117.52	$117.50	$117.50
Purchase #4	$45.97	4.277%	$47.9361	$47.94	$47.95	$47.90
Purchase #5	$229.78	6.296%	$244.2469	$244.25	$244.25	$244.20
Purchase #6	$7.34	7.407%	$7.8837	$7.88	$7.90	$7.90
Purchase #7	$128.92	10.433%	$142.3702	$142.37	$142.35	$142.40
7 purchase totals =	$799.96		$871.8052	$871.81	$871.80	$871.80