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	$10.73	8.311%	$11.6218	$11.62	$11.60	$11.60
Purchase #2	$195.88	13.754%	$222.8213	$222.82	$222.80	$222.80
Purchase #3	$79.44	4.515%	$83.0267	$83.03	$83.05	$83.00
Purchase #4	$184.33	8.184%	$199.4156	$199.42	$199.40	$199.40
Purchase #5	$185.57	5.627%	$196.012	$196.01	$196.00	$196.00
Purchase #6	$223.49	4.439%	$233.4107	$233.41	$233.40	$233.40
Purchase #7	$49.97	10.840%	$55.3867	$55.39	$55.40	$55.40
7 purchase totals =	$929.41		$1,001.6948	$1,001.70	$1,001.65	$1,001.60