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	$184.52	6.391%	$196.3127	$196.31	$196.30	$196.30
Purchase #2	$187.95	4.622%	$196.637	$196.64	$196.65	$196.60
Purchase #3	$29.49	5.741%	$31.183	$31.18	$31.20	$31.20
Purchase #4	$99.67	7.295%	$106.9409	$106.94	$106.95	$106.90
Purchase #5	$234.97	12.769%	$264.9733	$264.97	$264.95	$265.00
Purchase #6	$176.58	12.579%	$198.792	$198.79	$198.80	$198.80
Purchase #7	$78.55	10.109%	$86.4906	$86.49	$86.50	$86.50
7 purchase totals =	$991.73		$1,081.3295	$1,081.32	$1,081.35	$1,081.30