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	$213.71	11.569%	$238.4341	$238.43	$238.45	$238.40
Purchase #2	$81.45	3.319%	$84.1533	$84.15	$84.15	$84.20
Purchase #3	$72.91	11.455%	$81.2618	$81.26	$81.25	$81.30
Purchase #4	$156.60	7.267%	$167.9801	$167.98	$168.00	$168.00
Purchase #5	$152.75	7.714%	$164.5331	$164.53	$164.55	$164.50
Purchase #6	$158.82	8.673%	$172.5945	$172.59	$172.60	$172.60
Purchase #7	$71.30	8.448%	$77.3234	$77.32	$77.30	$77.30
7 purchase totals =	$907.54		$986.2803	$986.26	$986.30	$986.30