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	$149.63	12.758%	$168.7198	$168.72	$168.70	$168.70
Purchase #2	$47.68	7.819%	$51.4081	$51.41	$51.40	$51.40
Purchase #3	$32.76	12.175%	$36.7485	$36.75	$36.75	$36.70
Purchase #4	$83.89	7.425%	$90.1188	$90.12	$90.10	$90.10
Purchase #5	$213.66	8.133%	$231.037	$231.04	$231.05	$231.00
Purchase #6	$242.51	6.601%	$258.5181	$258.52	$258.50	$258.50
Purchase #7	$205.56	13.492%	$233.2942	$233.29	$233.30	$233.30
7 purchase totals =	$975.69		$1,069.8445	$1,069.85	$1,069.80	$1,069.70