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	$40.52	8.272%	$43.8718	$43.87	$43.85	$43.90
Purchase #2	$141.73	11.224%	$157.6378	$157.64	$157.65	$157.60
Purchase #3	$215.46	10.674%	$238.4582	$238.46	$238.45	$238.50
Purchase #4	$99.92	8.823%	$108.7359	$108.74	$108.75	$108.70
Purchase #5	$178.32	7.470%	$191.6405	$191.64	$191.65	$191.60
Purchase #6	$86.81	6.676%	$92.6054	$92.61	$92.60	$92.60
Purchase #7	$201.56	10.519%	$222.7621	$222.76	$222.75	$222.80
7 purchase totals =	$964.32		$1,055.7117	$1,055.72	$1,055.70	$1,055.70