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	$161.89	11.413%	$180.3665	$180.37	$180.35	$180.40
Purchase #2	$175.50	11.740%	$196.1037	$196.10	$196.10	$196.10
Purchase #3	$42.95	13.608%	$48.7946	$48.79	$48.80	$48.80
Purchase #4	$39.58	7.383%	$42.5022	$42.50	$42.50	$42.50
Purchase #5	$44.90	13.508%	$50.9651	$50.97	$50.95	$51.00
Purchase #6	$86.80	4.778%	$90.9473	$90.95	$90.95	$90.90
Purchase #7	$176.41	3.289%	$182.2121	$182.21	$182.20	$182.20
7 purchase totals =	$728.03		$791.8915	$791.89	$791.85	$791.90