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	$78.94	9.708%	$86.6035	$86.60	$86.60	$86.60
Purchase #2	$126.98	12.144%	$142.4005	$142.40	$142.40	$142.40
Purchase #3	$25.52	4.789%	$26.7422	$26.74	$26.75	$26.70
Purchase #4	$228.83	13.450%	$259.6076	$259.61	$259.60	$259.60
Purchase #5	$146.52	7.449%	$157.4343	$157.43	$157.45	$157.40
Purchase #6	$168.95	13.238%	$191.3156	$191.32	$191.30	$191.30
Purchase #7	$158.79	4.232%	$165.51	$165.51	$165.50	$165.50
7 purchase totals =	$934.53		$1,029.6137	$1,029.61	$1,029.60	$1,029.50