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	$94.26	9.545%	$103.2571	$103.26	$103.25	$103.30
Purchase #2	$245.31	13.464%	$278.3385	$278.34	$278.35	$278.30
Purchase #3	$238.66	11.443%	$265.9699	$265.97	$265.95	$266.00
Purchase #4	$105.76	5.322%	$111.3885	$111.39	$111.40	$111.40
Purchase #5	$64.37	10.233%	$70.957	$70.96	$70.95	$71.00
Purchase #6	$213.93	9.208%	$233.6287	$233.63	$233.65	$233.60
Purchase #7	$196.60	9.435%	$215.1492	$215.15	$215.15	$215.10
7 purchase totals =	$1,158.89		$1,278.6889	$1,278.70	$1,278.70	$1,278.70