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	$218.39	13.555%	$247.9928	$247.99	$248.00	$248.00
Purchase #2	$100.36	13.639%	$114.0481	$114.05	$114.05	$114.00
Purchase #3	$248.27	6.513%	$264.4398	$264.44	$264.45	$264.40
Purchase #4	$52.94	3.656%	$54.8755	$54.88	$54.90	$54.90
Purchase #5	$159.27	10.239%	$175.5777	$175.58	$175.60	$175.60
Purchase #6	$87.59	3.223%	$90.413	$90.41	$90.40	$90.40
Purchase #7	$148.51	13.341%	$168.3227	$168.32	$168.30	$168.30
7 purchase totals =	$1,015.33		$1,115.6696	$1,115.67	$1,115.70	$1,115.60