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	$150.97	3.256%	$155.8856	$155.89	$155.90	$155.90
Purchase #2	$161.44	3.171%	$166.5593	$166.56	$166.55	$166.60
Purchase #3	$139.57	13.617%	$158.5752	$158.58	$158.60	$158.60
Purchase #4	$192.88	11.699%	$215.445	$215.45	$215.45	$215.40
Purchase #5	$179.36	9.144%	$195.7607	$195.76	$195.75	$195.80
Purchase #6	$153.43	10.114%	$168.9479	$168.95	$168.95	$168.90
Purchase #7	$42.94	3.200%	$44.3141	$44.31	$44.30	$44.30
7 purchase totals =	$1,020.59		$1,105.4878	$1,105.50	$1,105.50	$1,105.50