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	$106.81	10.541%	$118.0688	$118.07	$118.05	$118.10
Purchase #2	$154.98	7.382%	$166.4206	$166.42	$166.40	$166.40
Purchase #3	$87.36	11.832%	$97.6964	$97.70	$97.70	$97.70
Purchase #4	$72.71	13.394%	$82.4488	$82.45	$82.45	$82.40
Purchase #5	$100.97	8.539%	$109.5918	$109.59	$109.60	$109.60
Purchase #6	$123.66	6.395%	$131.5681	$131.57	$131.55	$131.60
Purchase #7	$107.28	10.352%	$118.3856	$118.39	$118.40	$118.40
7 purchase totals =	$753.77		$824.1801	$824.19	$824.15	$824.20