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	$156.70	7.426%	$168.3365	$168.34	$168.35	$168.30
Purchase #2	$232.40	6.616%	$247.7756	$247.78	$247.80	$247.80
Purchase #3	$177.85	7.114%	$190.5022	$190.50	$190.50	$190.50
Purchase #4	$82.83	8.752%	$90.0793	$90.08	$90.10	$90.10
Purchase #5	$191.88	4.470%	$200.457	$200.46	$200.45	$200.50
Purchase #6	$107.50	3.589%	$111.3582	$111.36	$111.35	$111.40
Purchase #7	$141.61	3.148%	$146.0679	$146.07	$146.05	$146.10
7 purchase totals =	$1,090.77		$1,154.5767	$1,154.59	$1,154.60	$1,154.70