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	$64.54	10.693%	$71.4413	$71.44	$71.45	$71.40
Purchase #2	$241.59	13.747%	$274.8014	$274.80	$274.80	$274.80
Purchase #3	$94.64	11.372%	$105.4025	$105.40	$105.40	$105.40
Purchase #4	$71.50	4.218%	$74.5159	$74.52	$74.50	$74.50
Purchase #5	$36.90	3.463%	$38.1778	$38.18	$38.20	$38.20
Purchase #6	$174.88	13.620%	$198.6987	$198.70	$198.70	$198.70
Purchase #7	$175.33	13.563%	$199.11	$199.11	$199.10	$199.10
7 purchase totals =	$859.38		$962.1476	$962.15	$962.15	$962.10