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	$88.45	9.468%	$96.8244	$96.82	$96.80	$96.80
Purchase #2	$148.84	10.795%	$164.9073	$164.91	$164.90	$164.90
Purchase #3	$236.57	9.787%	$259.7231	$259.72	$259.70	$259.70
Purchase #4	$185.46	6.171%	$196.9047	$196.90	$196.90	$196.90
Purchase #5	$38.93	7.138%	$41.7088	$41.71	$41.70	$41.70
Purchase #6	$32.48	6.515%	$34.5961	$34.60	$34.60	$34.60
Purchase #7	$239.62	4.850%	$251.2416	$251.24	$251.25	$251.20
7 purchase totals =	$970.35		$1,045.9060	$1,045.90	$1,045.85	$1,045.80