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	$160.65	4.318%	$167.5869	$167.59	$167.60	$167.60
Purchase #2	$34.68	3.562%	$35.9153	$35.92	$35.90	$35.90
Purchase #3	$178.66	10.208%	$196.8976	$196.90	$196.90	$196.90
Purchase #4	$227.61	3.533%	$235.6515	$235.65	$235.65	$235.70
Purchase #5	$227.36	5.527%	$239.9262	$239.93	$239.95	$239.90
Purchase #6	$80.59	13.191%	$91.2206	$91.22	$91.20	$91.20
Purchase #7	$36.76	4.794%	$38.5223	$38.52	$38.50	$38.50
7 purchase totals =	$946.31		$1,005.7204	$1,005.73	$1,005.70	$1,005.70