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	$227.83	6.650%	$242.9807	$242.98	$243.00	$243.00
Purchase #2	$168.48	8.255%	$182.388	$182.39	$182.40	$182.40
Purchase #3	$106.35	11.785%	$118.8833	$118.88	$118.90	$118.90
Purchase #4	$140.67	13.312%	$159.396	$159.40	$159.40	$159.40
Purchase #5	$100.80	3.551%	$104.3794	$104.38	$104.40	$104.40
Purchase #6	$47.30	4.500%	$49.4285	$49.43	$49.45	$49.40
Purchase #7	$205.88	10.568%	$227.6374	$227.64	$227.65	$227.60
7 purchase totals =	$997.31		$1,085.0933	$1,085.10	$1,085.20	$1,085.10