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	$147.67	4.797%	$154.7537	$154.75	$154.75	$154.80
Purchase #2	$129.61	11.758%	$144.8495	$144.85	$144.85	$144.80
Purchase #3	$105.59	8.302%	$114.3561	$114.36	$114.35	$114.40
Purchase #4	$186.42	5.187%	$196.0896	$196.09	$196.10	$196.10
Purchase #5	$41.72	5.842%	$44.1573	$44.16	$44.15	$44.20
Purchase #6	$187.43	9.863%	$205.9162	$205.92	$205.90	$205.90
Purchase #7	$181.68	3.347%	$187.7608	$187.76	$187.75	$187.80
7 purchase totals =	$980.12		$1,047.8832	$1,047.89	$1,047.85	$1,048.00