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	$124.49	13.616%	$141.4406	$141.44	$141.45	$141.40
Purchase #2	$92.88	3.321%	$95.9645	$95.96	$95.95	$96.00
Purchase #3	$111.65	10.221%	$123.0617	$123.06	$123.05	$123.10
Purchase #4	$51.30	10.729%	$56.804	$56.80	$56.80	$56.80
Purchase #5	$85.57	3.519%	$88.5812	$88.58	$88.60	$88.60
Purchase #6	$126.85	10.340%	$139.9663	$139.97	$139.95	$140.00
Purchase #7	$136.47	12.680%	$153.7744	$153.77	$153.75	$153.80
7 purchase totals =	$729.21		$799.5927	$799.58	$799.55	$799.70