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	$96.94	9.242%	$105.8992	$105.90	$105.90	$105.90
Purchase #2	$120.66	6.138%	$128.0661	$128.07	$128.05	$128.10
Purchase #3	$188.32	6.584%	$200.719	$200.72	$200.70	$200.70
Purchase #4	$172.32	4.804%	$180.5983	$180.60	$180.60	$180.60
Purchase #5	$245.80	5.812%	$260.0859	$260.09	$260.10	$260.10
Purchase #6	$245.54	11.338%	$273.3793	$273.38	$273.40	$273.40
Purchase #7	$149.36	7.185%	$160.0915	$160.09	$160.10	$160.10
7 purchase totals =	$1,218.94		$1,308.8393	$1,308.85	$1,308.85	$1,308.90