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	$62.67	7.196%	$67.1797	$67.18	$67.20	$67.20
Purchase #2	$20.73	6.489%	$22.0752	$22.08	$22.10	$22.10
Purchase #3	$152.95	6.324%	$162.6226	$162.62	$162.60	$162.60
Purchase #4	$98.65	10.506%	$109.0142	$109.01	$109.00	$109.00
Purchase #5	$205.91	3.284%	$212.6721	$212.67	$212.65	$212.70
Purchase #6	$242.81	5.131%	$255.2686	$255.27	$255.25	$255.30
Purchase #7	$93.59	10.681%	$103.5863	$103.59	$103.60	$103.60
7 purchase totals =	$877.31		$932.4187	$932.42	$932.40	$932.50