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	$145.83	7.380%	$156.5923	$156.59	$156.60	$156.60
Purchase #2	$42.71	9.715%	$46.8593	$46.86	$46.85	$46.90
Purchase #3	$151.73	10.442%	$167.5736	$167.57	$167.55	$167.60
Purchase #4	$223.80	12.391%	$251.5311	$251.53	$251.55	$251.50
Purchase #5	$230.84	12.506%	$259.7089	$259.71	$259.70	$259.70
Purchase #6	$38.29	7.141%	$41.0243	$41.02	$41.00	$41.00
Purchase #7	$146.63	3.238%	$151.3779	$151.38	$151.40	$151.40
7 purchase totals =	$979.83		$1,074.6674	$1,074.66	$1,074.65	$1,074.70