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	$94.50	10.611%	$104.5274	$104.53	$104.55	$104.50
Purchase #2	$184.63	6.204%	$196.0844	$196.08	$196.10	$196.10
Purchase #3	$80.79	5.612%	$85.3239	$85.32	$85.30	$85.30
Purchase #4	$187.39	4.678%	$196.1561	$196.16	$196.15	$196.20
Purchase #5	$193.59	4.180%	$201.6821	$201.68	$201.70	$201.70
Purchase #6	$9.94	3.860%	$10.3237	$10.32	$10.30	$10.30
Purchase #7	$167.72	6.433%	$178.5094	$178.51	$178.50	$178.50
7 purchase totals =	$918.56		$972.6070	$972.60	$972.60	$972.60