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	$177.86	3.356%	$183.829	$183.83	$183.85	$183.80
Purchase #2	$186.92	8.779%	$203.3297	$203.33	$203.35	$203.30
Purchase #3	$218.66	3.139%	$225.5237	$225.52	$225.50	$225.50
Purchase #4	$227.77	4.635%	$238.3271	$238.33	$238.35	$238.30
Purchase #5	$118.85	3.786%	$123.3497	$123.35	$123.35	$123.30
Purchase #6	$115.98	6.186%	$123.1545	$123.15	$123.15	$123.20
Purchase #7	$144.29	8.286%	$156.2459	$156.25	$156.25	$156.20
7 purchase totals =	$1,190.33		$1,253.7596	$1,253.76	$1,253.80	$1,253.60