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	$99.33	11.718%	$110.9695	$110.97	$110.95	$111.00
Purchase #2	$56.52	6.722%	$60.3193	$60.32	$60.30	$60.30
Purchase #3	$81.33	11.370%	$90.5772	$90.58	$90.60	$90.60
Purchase #4	$93.81	7.473%	$100.8204	$100.82	$100.80	$100.80
Purchase #5	$208.95	3.139%	$215.5089	$215.51	$215.50	$215.50
Purchase #6	$218.47	7.593%	$235.0584	$235.06	$235.05	$235.10
Purchase #7	$160.74	12.227%	$180.3937	$180.39	$180.40	$180.40
7 purchase totals =	$919.15		$993.6474	$993.65	$993.60	$993.70