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	$202.94	6.131%	$215.3823	$215.38	$215.40	$215.40
Purchase #2	$186.69	10.184%	$205.7025	$205.70	$205.70	$205.70
Purchase #3	$233.70	7.210%	$250.5498	$250.55	$250.55	$250.50
Purchase #4	$35.55	11.541%	$39.6528	$39.65	$39.65	$39.70
Purchase #5	$25.95	8.180%	$28.0727	$28.07	$28.05	$28.10
Purchase #6	$91.84	8.618%	$99.7548	$99.75	$99.75	$99.80
Purchase #7	$224.76	13.521%	$255.1498	$255.15	$255.15	$255.10
7 purchase totals =	$1,001.43		$1,094.2647	$1,094.25	$1,094.25	$1,094.30