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	$235.81	12.745%	$265.864	$265.86	$265.85	$265.90
Purchase #2	$194.30	7.763%	$209.3835	$209.38	$209.40	$209.40
Purchase #3	$84.47	13.408%	$95.7957	$95.80	$95.80	$95.80
Purchase #4	$192.33	12.240%	$215.8712	$215.87	$215.85	$215.90
Purchase #5	$152.65	4.454%	$159.449	$159.45	$159.45	$159.40
Purchase #6	$12.80	6.116%	$13.5828	$13.58	$13.60	$13.60
Purchase #7	$164.84	12.459%	$185.3774	$185.38	$185.40	$185.40
7 purchase totals =	$1,037.20		$1,145.3236	$1,145.32	$1,145.35	$1,145.40