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	$195.92	13.331%	$222.0381	$222.04	$222.05	$222.00
Purchase #2	$137.32	7.508%	$147.63	$147.63	$147.65	$147.60
Purchase #3	$217.85	9.137%	$237.755	$237.76	$237.75	$237.80
Purchase #4	$99.29	6.596%	$105.8392	$105.84	$105.85	$105.80
Purchase #5	$101.38	8.372%	$109.8675	$109.87	$109.85	$109.90
Purchase #6	$126.65	7.757%	$136.4742	$136.47	$136.45	$136.50
Purchase #7	$91.43	4.513%	$95.5562	$95.56	$95.55	$95.60
7 purchase totals =	$969.84		$1,055.1602	$1,055.17	$1,055.15	$1,055.20