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	$158.88	4.577%	$166.1519	$166.15	$166.15	$166.20
Purchase #2	$61.44	4.799%	$64.3885	$64.39	$64.40	$64.40
Purchase #3	$25.37	8.767%	$27.5942	$27.59	$27.60	$27.60
Purchase #4	$225.55	7.699%	$242.9151	$242.92	$242.90	$242.90
Purchase #5	$135.56	5.378%	$142.8504	$142.85	$142.85	$142.90
Purchase #6	$159.45	11.753%	$178.1902	$178.19	$178.20	$178.20
Purchase #7	$224.97	13.483%	$255.3027	$255.30	$255.30	$255.30
7 purchase totals =	$991.22		$1,077.3930	$1,077.39	$1,077.40	$1,077.50