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	$190.98	5.416%	$201.3235	$201.32	$201.30	$201.30
Purchase #2	$135.40	9.259%	$147.9367	$147.94	$147.95	$147.90
Purchase #3	$173.43	13.395%	$196.6609	$196.66	$196.65	$196.70
Purchase #4	$52.76	7.329%	$56.6268	$56.63	$56.65	$56.60
Purchase #5	$155.58	10.130%	$171.3403	$171.34	$171.35	$171.30
Purchase #6	$206.59	10.793%	$228.8873	$228.89	$228.90	$228.90
Purchase #7	$66.71	8.224%	$72.1962	$72.20	$72.20	$72.20
7 purchase totals =	$981.45		$1,074.9717	$1,074.98	$1,075.00	$1,074.90