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	$105.90	5.588%	$111.8177	$111.82	$111.80	$111.80
Purchase #2	$176.51	3.251%	$182.2483	$182.25	$182.25	$182.20
Purchase #3	$101.31	5.557%	$106.9398	$106.94	$106.95	$106.90
Purchase #4	$184.83	8.711%	$200.9305	$200.93	$200.95	$200.90
Purchase #5	$94.89	3.799%	$98.4949	$98.49	$98.50	$98.50
Purchase #6	$12.84	8.154%	$13.887	$13.89	$13.90	$13.90
Purchase #7	$183.34	3.261%	$189.3187	$189.32	$189.30	$189.30
7 purchase totals =	$859.62		$903.6369	$903.64	$903.65	$903.50