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	$44.72	4.858%	$46.8925	$46.89	$46.90	$46.90
Purchase #2	$50.73	6.832%	$54.1959	$54.20	$54.20	$54.20
Purchase #3	$219.65	5.372%	$231.4496	$231.45	$231.45	$231.40
Purchase #4	$30.48	3.423%	$31.5233	$31.52	$31.50	$31.50
Purchase #5	$217.34	13.699%	$247.1134	$247.11	$247.10	$247.10
Purchase #6	$248.30	12.381%	$279.042	$279.04	$279.05	$279.00
Purchase #7	$167.57	4.473%	$175.0654	$175.07	$175.05	$175.10
7 purchase totals =	$978.79		$1,065.2821	$1,065.28	$1,065.25	$1,065.20