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	$238.92	10.477%	$263.9516	$263.95	$263.95	$264.00
Purchase #2	$63.45	13.535%	$72.038	$72.04	$72.05	$72.00
Purchase #3	$77.81	12.851%	$87.8094	$87.81	$87.80	$87.80
Purchase #4	$166.86	9.521%	$182.7467	$182.75	$182.75	$182.70
Purchase #5	$232.44	3.508%	$240.594	$240.59	$240.60	$240.60
Purchase #6	$87.41	13.139%	$98.8948	$98.89	$98.90	$98.90
Purchase #7	$66.25	10.648%	$73.3043	$73.30	$73.30	$73.30
7 purchase totals =	$933.14		$1,019.3388	$1,019.33	$1,019.35	$1,019.30