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	$115.57	10.859%	$128.1197	$128.12	$128.10	$128.10
Purchase #2	$232.47	3.455%	$240.5018	$240.50	$240.50	$240.50
Purchase #3	$56.56	10.696%	$62.6097	$62.61	$62.60	$62.60
Purchase #4	$40.75	11.867%	$45.5858	$45.59	$45.60	$45.60
Purchase #5	$43.92	10.638%	$48.5922	$48.59	$48.60	$48.60
Purchase #6	$229.76	6.512%	$244.722	$244.72	$244.70	$244.70
Purchase #7	$23.73	10.820%	$26.2976	$26.30	$26.30	$26.30
7 purchase totals =	$742.76		$796.4288	$796.43	$796.40	$796.40