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	$149.40	11.420%	$166.4615	$166.46	$166.45	$166.50
Purchase #2	$130.25	13.558%	$147.9093	$147.91	$147.90	$147.90
Purchase #3	$168.77	10.577%	$186.6208	$186.62	$186.60	$186.60
Purchase #4	$105.96	3.629%	$109.8053	$109.81	$109.80	$109.80
Purchase #5	$180.82	13.814%	$205.7985	$205.80	$205.80	$205.80
Purchase #6	$171.47	3.551%	$177.5589	$177.56	$177.55	$177.60
Purchase #7	$23.29	10.676%	$25.7764	$25.78	$25.80	$25.80
7 purchase totals =	$929.96		$1,019.9307	$1,019.94	$1,019.90	$1,020.00