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	$103.59	8.149%	$112.0315	$112.03	$112.05	$112.00
Purchase #2	$173.42	10.447%	$191.5372	$191.54	$191.55	$191.50
Purchase #3	$75.43	9.715%	$82.758	$82.76	$82.75	$82.80
Purchase #4	$168.79	13.822%	$192.1202	$192.12	$192.10	$192.10
Purchase #5	$153.61	11.501%	$171.2767	$171.28	$171.30	$171.30
Purchase #6	$47.70	3.508%	$49.3733	$49.37	$49.35	$49.40
Purchase #7	$173.71	6.768%	$185.4667	$185.47	$185.45	$185.50
7 purchase totals =	$896.25		$984.5636	$984.57	$984.55	$984.60