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	$200.28	13.643%	$227.6042	$227.60	$227.60	$227.60
Purchase #2	$84.57	12.761%	$95.362	$95.36	$95.35	$95.40
Purchase #3	$171.86	9.818%	$188.7332	$188.73	$188.75	$188.70
Purchase #4	$125.73	13.418%	$142.6005	$142.60	$142.60	$142.60
Purchase #5	$123.98	11.245%	$137.9216	$137.92	$137.90	$137.90
Purchase #6	$43.25	7.653%	$46.5599	$46.56	$46.55	$46.60
Purchase #7	$231.55	4.817%	$242.7038	$242.70	$242.70	$242.70
7 purchase totals =	$981.22		$1,081.4852	$1,081.47	$1,081.45	$1,081.50