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	$201.88	3.821%	$209.5938	$209.59	$209.60	$209.60
Purchase #2	$9.93	6.381%	$10.5636	$10.56	$10.55	$10.60
Purchase #3	$157.39	13.401%	$178.4818	$178.48	$178.50	$178.50
Purchase #4	$170.69	11.333%	$190.0343	$190.03	$190.05	$190.00
Purchase #5	$227.55	9.152%	$248.3754	$248.38	$248.40	$248.40
Purchase #6	$39.52	7.227%	$42.3761	$42.38	$42.40	$42.40
Purchase #7	$42.37	7.134%	$45.3927	$45.39	$45.40	$45.40
7 purchase totals =	$849.33		$924.8177	$924.81	$924.90	$924.90