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	$191.76	10.726%	$212.3282	$212.33	$212.35	$212.30
Purchase #2	$193.63	3.303%	$200.0256	$200.03	$200.05	$200.00
Purchase #3	$115.82	6.706%	$123.5869	$123.59	$123.60	$123.60
Purchase #4	$125.89	12.300%	$141.3745	$141.37	$141.35	$141.40
Purchase #5	$15.73	10.166%	$17.3291	$17.33	$17.35	$17.30
Purchase #6	$132.66	3.847%	$137.7634	$137.76	$137.75	$137.80
Purchase #7	$120.46	9.378%	$131.7567	$131.76	$131.75	$131.80
7 purchase totals =	$895.95		$964.1644	$964.17	$964.20	$964.20