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	$135.38	9.667%	$148.4672	$148.47	$148.45	$148.50
Purchase #2	$200.27	7.700%	$215.6908	$215.69	$215.70	$215.70
Purchase #3	$143.45	8.861%	$156.1611	$156.16	$156.15	$156.20
Purchase #4	$161.72	6.336%	$171.9666	$171.97	$171.95	$172.00
Purchase #5	$109.56	7.150%	$117.3935	$117.39	$117.40	$117.40
Purchase #6	$148.46	10.799%	$164.4922	$164.49	$164.50	$164.50
Purchase #7	$202.83	6.265%	$215.5373	$215.54	$215.55	$215.50
7 purchase totals =	$1,101.67		$1,189.7087	$1,189.71	$1,189.70	$1,189.80