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	$84.71	7.846%	$91.3563	$91.36	$91.35	$91.40
Purchase #2	$201.29	6.436%	$214.245	$214.25	$214.25	$214.20
Purchase #3	$78.43	10.336%	$86.5365	$86.54	$86.55	$86.50
Purchase #4	$190.52	7.777%	$205.3367	$205.34	$205.35	$205.30
Purchase #5	$226.62	10.456%	$250.3154	$250.32	$250.30	$250.30
Purchase #6	$172.91	10.110%	$190.3912	$190.39	$190.40	$190.40
Purchase #7	$20.33	7.324%	$21.819	$21.82	$21.80	$21.80
7 purchase totals =	$974.81		$1,060.0001	$1,060.02	$1,060.00	$1,059.90