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	$50.59	6.422%	$53.8389	$53.84	$53.85	$53.80
Purchase #2	$87.83	9.695%	$96.3451	$96.35	$96.35	$96.30
Purchase #3	$90.84	8.390%	$98.4615	$98.46	$98.45	$98.50
Purchase #4	$20.28	5.631%	$21.422	$21.42	$21.40	$21.40
Purchase #5	$194.90	11.317%	$216.9568	$216.96	$216.95	$217.00
Purchase #6	$59.94	3.191%	$61.8527	$61.85	$61.85	$61.90
Purchase #7	$187.62	12.451%	$210.9806	$210.98	$211.00	$211.00
7 purchase totals =	$692.00		$759.8576	$759.86	$759.85	$759.90