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	$76.54	12.458%	$86.0754	$86.08	$86.10	$86.10
Purchase #2	$126.36	13.503%	$143.4224	$143.42	$143.40	$143.40
Purchase #3	$93.92	10.192%	$103.4923	$103.49	$103.50	$103.50
Purchase #4	$104.72	13.281%	$118.6279	$118.63	$118.65	$118.60
Purchase #5	$137.75	3.249%	$142.2255	$142.23	$142.25	$142.20
Purchase #6	$18.47	7.829%	$19.916	$19.92	$19.90	$19.90
Purchase #7	$239.42	13.425%	$271.5621	$271.56	$271.55	$271.60
7 purchase totals =	$797.18		$885.3216	$885.33	$885.35	$885.30