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	$213.50	13.468%	$242.2542	$242.25	$242.25	$242.30
Purchase #2	$78.70	13.775%	$89.5409	$89.54	$89.55	$89.50
Purchase #3	$247.50	4.344%	$258.2514	$258.25	$258.25	$258.30
Purchase #4	$139.52	10.204%	$153.7566	$153.76	$153.75	$153.80
Purchase #5	$143.32	13.708%	$162.9663	$162.97	$162.95	$163.00
Purchase #6	$85.80	12.150%	$96.2247	$96.22	$96.20	$96.20
Purchase #7	$169.77	7.764%	$182.9509	$182.95	$182.95	$183.00
7 purchase totals =	$1,078.11		$1,185.9450	$1,185.94	$1,185.90	$1,186.10