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	$9.63	12.282%	$10.8128	$10.81	$10.80	$10.80
Purchase #2	$243.74	4.786%	$255.4054	$255.41	$255.40	$255.40
Purchase #3	$70.52	8.174%	$76.2843	$76.28	$76.30	$76.30
Purchase #4	$34.36	7.723%	$37.0136	$37.01	$37.00	$37.00
Purchase #5	$47.83	10.127%	$52.6737	$52.67	$52.65	$52.70
Purchase #6	$187.63	4.757%	$196.5556	$196.56	$196.55	$196.60
Purchase #7	$111.90	13.353%	$126.842	$126.84	$126.85	$126.80
7 purchase totals =	$705.61		$755.5874	$755.58	$755.55	$755.60