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	$173.40	10.565%	$191.7197	$191.72	$191.70	$191.70
Purchase #2	$56.39	3.628%	$58.4358	$58.44	$58.45	$58.40
Purchase #3	$191.38	4.813%	$200.5911	$200.59	$200.60	$200.60
Purchase #4	$42.78	3.556%	$44.3013	$44.30	$44.30	$44.30
Purchase #5	$109.38	4.770%	$114.5974	$114.60	$114.60	$114.60
Purchase #6	$173.35	4.151%	$180.5458	$180.55	$180.55	$180.50
Purchase #7	$156.60	7.402%	$168.1915	$168.19	$168.20	$168.20
7 purchase totals =	$903.28		$958.3826	$958.39	$958.40	$958.30