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	$163.55	6.229%	$173.7375	$173.74	$173.75	$173.70
Purchase #2	$157.27	4.630%	$164.5516	$164.55	$164.55	$164.60
Purchase #3	$28.41	12.727%	$32.0257	$32.03	$32.05	$32.00
Purchase #4	$182.38	7.742%	$196.4999	$196.50	$196.50	$196.50
Purchase #5	$35.77	5.667%	$37.7971	$37.80	$37.80	$37.80
Purchase #6	$159.32	3.757%	$165.3057	$165.31	$165.30	$165.30
Purchase #7	$177.72	12.602%	$200.1163	$200.12	$200.10	$200.10
7 purchase totals =	$904.42		$970.0338	$970.05	$970.05	$970.00