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	$142.78	11.429%	$159.0983	$159.10	$159.10	$159.10
Purchase #2	$155.51	13.333%	$176.2441	$176.24	$176.25	$176.20
Purchase #3	$227.66	3.173%	$234.8837	$234.88	$234.90	$234.90
Purchase #4	$168.59	12.274%	$189.2827	$189.28	$189.30	$189.30
Purchase #5	$11.50	8.155%	$12.4378	$12.44	$12.45	$12.40
Purchase #6	$219.62	13.871%	$250.0835	$250.08	$250.10	$250.10
Purchase #7	$39.61	3.112%	$40.8427	$40.84	$40.85	$40.80
7 purchase totals =	$965.27		$1,062.8728	$1,062.86	$1,062.95	$1,062.80