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	$32.79	11.190%	$36.4592	$36.46	$36.45	$36.50
Purchase #2	$242.56	3.455%	$250.9404	$250.94	$250.95	$250.90
Purchase #3	$11.83	7.625%	$12.732	$12.73	$12.75	$12.70
Purchase #4	$191.83	4.567%	$200.5909	$200.59	$200.60	$200.60
Purchase #5	$83.55	3.819%	$86.7408	$86.74	$86.75	$86.70
Purchase #6	$233.73	3.268%	$241.3683	$241.37	$241.35	$241.40
Purchase #7	$63.72	13.767%	$72.4923	$72.49	$72.50	$72.50
7 purchase totals =	$860.01		$901.3239	$901.32	$901.35	$901.30