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	$245.44	11.581%	$273.8644	$273.86	$273.85	$273.90
Purchase #2	$174.81	4.458%	$182.603	$182.60	$182.60	$182.60
Purchase #3	$36.34	11.570%	$40.5445	$40.54	$40.55	$40.50
Purchase #4	$115.47	13.643%	$131.2236	$131.22	$131.20	$131.20
Purchase #5	$205.92	11.513%	$229.6276	$229.63	$229.65	$229.60
Purchase #6	$230.83	11.612%	$257.634	$257.63	$257.65	$257.60
Purchase #7	$40.40	10.108%	$44.4836	$44.48	$44.50	$44.50
7 purchase totals =	$1,049.21		$1,159.9807	$1,159.96	$1,160.00	$1,159.90