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	$229.94	4.825%	$241.0346	$241.03	$241.05	$241.00
Purchase #2	$152.73	4.685%	$159.8854	$159.89	$159.90	$159.90
Purchase #3	$73.47	7.155%	$78.7268	$78.73	$78.75	$78.70
Purchase #4	$249.63	6.304%	$265.3667	$265.37	$265.35	$265.40
Purchase #5	$34.66	6.268%	$36.8325	$36.83	$36.85	$36.80
Purchase #6	$147.57	3.307%	$152.4501	$152.45	$152.45	$152.50
Purchase #7	$153.77	11.178%	$170.9584	$170.96	$170.95	$171.00
7 purchase totals =	$1,041.77		$1,105.2545	$1,105.26	$1,105.30	$1,105.30