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	$167.73	5.761%	$177.3929	$177.39	$177.40	$177.40
Purchase #2	$52.93	7.521%	$56.9109	$56.91	$56.90	$56.90
Purchase #3	$213.45	9.559%	$233.8537	$233.85	$233.85	$233.90
Purchase #4	$202.93	6.517%	$216.1549	$216.15	$216.15	$216.20
Purchase #5	$49.54	10.510%	$54.7467	$54.75	$54.75	$54.70
Purchase #6	$30.43	6.745%	$32.4825	$32.48	$32.50	$32.50
Purchase #7	$215.69	13.812%	$245.4811	$245.48	$245.50	$245.50
7 purchase totals =	$932.70		$1,017.0227	$1,017.01	$1,017.05	$1,017.10