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	$185.84	7.739%	$200.2222	$200.22	$200.20	$200.20
Purchase #2	$185.87	3.552%	$192.4721	$192.47	$192.45	$192.50
Purchase #3	$166.66	9.859%	$183.091	$183.09	$183.10	$183.10
Purchase #4	$99.38	4.568%	$103.9197	$103.92	$103.90	$103.90
Purchase #5	$83.84	7.651%	$90.2546	$90.25	$90.25	$90.30
Purchase #6	$176.97	8.787%	$192.5204	$192.52	$192.50	$192.50
Purchase #7	$167.30	4.664%	$175.1029	$175.10	$175.10	$175.10
7 purchase totals =	$1,065.86		$1,137.5829	$1,137.57	$1,137.50	$1,137.60