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	$45.45	13.550%	$51.6085	$51.61	$51.60	$51.60
Purchase #2	$45.31	13.136%	$51.2619	$51.26	$51.25	$51.30
Purchase #3	$124.67	9.670%	$136.7256	$136.73	$136.75	$136.70
Purchase #4	$40.59	9.560%	$44.4704	$44.47	$44.45	$44.50
Purchase #5	$211.63	3.287%	$218.5863	$218.59	$218.60	$218.60
Purchase #6	$93.66	8.773%	$101.8768	$101.88	$101.90	$101.90
Purchase #7	$86.80	4.283%	$90.5176	$90.52	$90.50	$90.50
7 purchase totals =	$648.11		$695.0471	$695.06	$695.05	$695.10