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	$35.64	3.180%	$36.7734	$36.77	$36.75	$36.80
Purchase #2	$79.63	8.492%	$86.3922	$86.39	$86.40	$86.40
Purchase #3	$100.40	7.681%	$108.1117	$108.11	$108.10	$108.10
Purchase #4	$152.89	9.111%	$166.8198	$166.82	$166.80	$166.80
Purchase #5	$175.46	9.525%	$192.1726	$192.17	$192.15	$192.20
Purchase #6	$137.84	4.721%	$144.3474	$144.35	$144.35	$144.30
Purchase #7	$250.82	9.605%	$274.9113	$274.91	$274.90	$274.90
7 purchase totals =	$932.68		$1,009.5284	$1,009.52	$1,009.45	$1,009.50